Light emitting stacked structure and display device having the same

ABSTRACT

A display device including a substrate, a light emitting stacked structure disposed on the substrate and including a plurality of epitaxial sub-units disposed one over another, a first adhesive layer bonding the epitaxial sub-units to the substrate; and a line part disposed on the substrate and configured to apply a light emitting signal to each of the epitaxial sub-units, in which the light emitting stacked structure is configured to provide light having various colors by a combination of light emitted from each of the epitaxial sub-units, and the first adhesive layer includes a conductive and non-transparent material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.17/847,105, filed on Jun. 22, 2022, which is a Continuation of U.S.patent application Ser. No. 16/228,621, filed on Dec. 20, 2018, nowissued as U.S. Pat. No. 11,522,006, which claims priority from and thebenefit of the U.S. Provisional Application No. 62/609,186, filed onDec. 21, 2017, and the U.S. Provisional Application No. 62/618,573,filed on Jan. 17, 2018, which are hereby incorporated by reference forall purposes as if fully set forth herein.

BACKGROUND Field

Exemplary embodiments of the invention relate to a light emittingstacked structure and a display device having the same and, morespecifically, to a micro light emitting device having a stackedstructure and a display device having the same.

Discussion of the Background

A display device that implements an image using a light emitting diode(LED) has been recently developed. The display device employing thelight emitting diode may include red, green, and blue light emittingdiodes individually grown on a substrate.

As an inorganic light source, light emitting diodes have been used invarious technical fields, such as displays, vehicular lamps, generallighting, and the like. With advantages of long lifespan, low powerconsumption, and high response speed, light emitting diodes have beenrapidly replacing an existing light source.

Light emitting diodes have been mainly used as a backlight light sourcein a display apparatus. However, a micro-LED display has been developedas a next generation display that is capable of implementing an imagedirectly using the light emitting diodes.

In general, a display apparatus implements various colors by using mixedcolors of blue, green and red light. The display apparatus includespixels each having subpixels that correspond to blue, green, and redcolors, and a color of a certain pixel may be determined based on thecolors of the sub-pixels therein, and an image can be displayed throughcombination of the pixels.

In a micro-LED display, micro-LEDs corresponding to each subpixel arearranged on a two-dimensional plane. Therefore, a large number of microLEDs are required to be disposed on one substrate. However, themicro-LED has a very small size with a surface area of about 10,000square μm or less, and thus, there are various problems due to thissmall size. In particular, it is difficult to mount the micro-LEDs on adisplay panel due to its small size, especially as over hundreds ofthousands or millions are required.

In addition, there is a need for a high-resolution and full-colordisplay device, as well as for a display device having a high level ofcolor purity and color reproducibility that can be manufactured in asimplified method.

The above information disclosed in this Background section is only forunderstanding of the background of the inventive concepts, and,therefore, it may contain information that does not constitute priorart.

SUMMARY

Light emitting stacked structures constructed according to theprinciples and some exemplary implementations of the invention arecapable of increasing a light emitting area of each subpixel withoutincreasing the pixel area.

Light emitting diodes and display using the light emitting diodes, e.g.,micro LEDs, constructed according to the principles and some exemplaryimplementations of the invention have a simple structure that is capableof being manufactured in streamlined steps. For example, a plurality ofpixels may be formed at the wafer level by wafer bonding, therebyeliminating the need for individual mounting of light emitting diodes.

Additional features of the inventive concepts will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the inventive concepts.

A light emitting stacked structure according to an exemplary embodimentincludes a plurality of epitaxial sub-units disposed one over another,each of the epitaxial sub-units configured to emit different coloredlight, in which each epitaxial sub-unit has a light emitting area thatoverlaps one another, and at least one epitaxial sub-unit has an areadifferent from the area of another epitaxial sub-unit.

The area of each epitaxial sub-unit may decrease along a firstdirection.

Between two adjacent epitaxial sub-units, an upper epitaxial sub-unitmay completely overlap a lower epitaxial sub-unit having a larger area.

Light emitted from each epitaxial sub-unit may have different energybands from each other, and the energy bands may increase along a firstdirection.

The epitaxial sub-units may be independently drivable.

Light emitted from a lower epitaxial sub-unit may be configured to beemitted to the outside of the light emitted stacked structure by passingthrough an upper epitaxial sub-unit disposed on the lower epitaxialsub-unit.

The upper epitaxial sub-unit may be configured to transmit at leastabout 80% of light emitted from the lower epitaxial sub-unit.

The epitaxial sub-units may include a first epitaxial stack configuredto emit a first color light, a second epitaxial stack disposed on thefirst epitaxial stack and configured to emit a second color light havinga wavelength band different from the first color light, and a thirdepitaxial stack disposed on the second epitaxial stack and configured toemit a third color light having a wavelength band different from thefirst and second color lights.

The first, second, and third color lights may be a red light, a greenlight, and a blue light, respectively.

Each of the first, second, and third epitaxial stacks may include ap-type semiconductor layer, an active layer disposed on the p-typesemiconductor layer, and an n-type semiconductor layer disposed on theactive layer.

The light emitting stacked structure may further include first, second,and third p-type contact electrodes connected to the p-typesemiconductor layers of the first, second, and third epitaxial stacks,respectively.

The light emitting stacked structure may further include a substratedisposed under the first epitaxial stack, in which the first p-typecontact electrode may be disposed between the substrate and the firstepitaxial stack.

The light emitting stacked structure may further include first, second,and third n-type contact electrodes connected to the n-typesemiconductor layers of the first, second, and third epitaxial stacks,respectively.

The light emitting stacked structure may further include a common lineapplying a common voltage to the first, second, and third p-type contactelectrodes, and first, second, and third light emitting signal linesapplying a light emitting signal to the first, second, and third n-typecontact electrodes, respectively.

The light emitting stacked structure may further include at least one ofa first wavelength pass filter disposed between the first epitaxialstack and the second epitaxial stack and a second wavelength pass filterdisposed between the second epitaxial stack and the third epitaxialstack.

The light emitting diode pixel may include a micro LED having a surfacearea less than about 10,000 square μm.

At least one of the first, second, and third epitaxial stacks may have aconcave-convex pattern formed on one surface thereof.

A display device according to an exemplary embodiment includes aplurality of pixels, at least one of the pixels including a lightemitting stacked structure including a plurality of epitaxial sub-unitsdisposed one over another, each of the epitaxial sub-units configured toemit different colored light, in which each epitaxial sub-unit has alight emitting area that overlaps one another, and at least oneepitaxial sub-unit has an area different from the area of anotherepitaxial sub-unit.

The display device may be configured to be driven in a passive matrixmanner.

The display device may be configured to be driven in an active matrixmanner.

A light emitting diode pixel for a display according to an exemplaryembodiment includes a first LED sub-unit, a second LED sub-unit disposedon a first portion of the first LED sub-unit, and a third LED sub-unitdisposed on a second portion of the second LED sub-unit, in which eachof the first, second, and third LED sub-units include a firstconductivity type semiconductor layer and a second conductivity typesemiconductor layer, light generated from the first LED sub-unit isconfigured to be emitted outside of the light emitting diode pixelthrough a third portion of the first LED sub-unit different from thefirst portion, and light s generated from the second LED sub-unit isconfigured to be emitted outside of the light emitting diode pixelthrough a fourth portion of the second LED sub-unit different from thesecond portion.

The first LED sub-unit, the second LED sub-unit, and the third LEDsub-unit may be configured to emit light having different wavelengthsfrom each other, respectively.

The first, second, and third LED sub-units may include first LED stack,second LED stack, and third LED stack configured to emit red light,green light and blue light, respectively.

The light emitting diode pixel may further include a first reflectionlayer interposed between the first LED stack and the second LED stack toreflect light emitted from the first LED stack back to the first LEDstack, and a second reflection layer interposed between the second LEDstack and the third LED stack to reflect light emitted from the secondLED stack back to the second LED stack.

The light emitting diode pixel may further include a first transparentinsulation layer interposed between the first LED stack and the firstreflection layer, and a second transparent insulation layer interposedbetween the second LED stack and the second reflection layer.

The light emitting diode pixel may further include a first bonding layerinterposed between the first reflection layer and the second LED stack,and a second bonding layer interposed between the second reflectionlayer and the third LED stack.

Each of the first and second bonding layers may include metal.

The light emitting diode pixel may further include a first upper ohmicelectrode contacting the first conductivity type semiconductor layer ofthe first LED sub-unit, a first lower ohmic electrode contacting thesecond conductivity type semiconductor layer of the first LED sub-unit,a second upper ohmic electrode contacting the first conductivity typesemiconductor layer of the second LED sub-unit, a second lower ohmicelectrode contacting the second conductivity type semiconductor layer ofthe second LED sub-unit, a third upper ohmic electrode contacting thefirst conductivity type semiconductor layer of the third LED sub-unit,and a third lower ohmic electrode contacting the second conductivitytype semiconductor layer of the third LED sub-unit, in which the firstupper ohmic electrode may contact the first conductivity typesemiconductor layer of the first LED sub-unit in a portion of the firstLED sub-unit different from the first portion, and the second upperohmic electrode may contact the first conductivity type semiconductorlayer of the second LED sub-unit in a portion of the second LED sub-unitdifferent from the second portion.

The first lower ohmic electrode may include a first reflective layerdisposed under the first LED sub-unit.

The first lower ohmic electrode, the second lower ohmic electrode, andthe third lower ohmic electrode may be electrically connected to acommon line.

Each of the second lower ohmic electrode and the third lower ohmicelectrode may include a second reflective layer and a third reflectivelayer, respectively.

The first reflective layer may be configured to reflect light emittedfrom the first LED sub-unit, and the second reflective layer isconfigured to reflect light emitted from the second LED sub-unit.

The light emitting diode pixel may include a micro LED having a surfacearea less than about 10,000 square μm.

The first LED sub-unit may be configured to emit any one of red, green,and blue light, the second LED sub-unit may be configured to emit anyone of red, green, and blue light different from light emitted from thefirst LED sub-unit, and the third LED sub-unit may be configured to emitany one of red, green, and blue light different from light emitted fromthe first and second LED sub-units.

The third portion of the first LED, the fourth portion of the second LEDsub-unit, and the third LED sub-unit may not overlap each other.

At least one of the first, second, and third upper ohmic electrodes mayinclude a pad portion and a projection extending therefrom.

The pad portion may have a substantially circular shape, and theprojection may have a substantially elongated shape.

The projections of the first, second, and third LED stub-units may besubstantially parallel to each other in a plan view.

The first LED sub-unit may surround the third LED sub-unit in a planview.

A display apparatus may include a plurality of pixels arranged on asupport substrate, at least one of the pixels including the lightemitting diode pixel according to an exemplary embodiment.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of theinvention, and together with the description serve to explain theinventive concepts.

FIG. 1 is a schematic cross-sectional view of a light emitting stackedstructure constructed according to an exemplary embodiment.

FIG. 2 is a cross-sectional view of a light emitting stacked structureaccording to an exemplary embodiment.

FIG. 3 is a schematic cross-sectional view of a light emitting stackedstructure according to an exemplary embodiment.

FIG. 4 is a plan view of a display device according to an exemplaryembodiment.

FIG. 5 is an enlarged plan view of portion P1 of FIG. 4 .

FIG. 6 is a block diagram of a display device according to an exemplaryembodiment.

FIG. 7 is a circuit diagram of one pixel for a passive matrix typedisplay device according to an exemplary embodiment.

FIG. 8 is a circuit diagram of one pixel for an active matrix typedisplay device according to an exemplary embodiment.

FIG. 9 is a plan view of a pixel according to an exemplary embodiment.

FIG. 10 is a cross-sectional view taken along line I-I′ of FIG. 9 .

FIGS. 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, and 33 are plan viewsillustrating a method of forming first, second, and third epitaxialstacks according to an exemplary embodiment.

FIGS. 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, and 34 arecross-sectional views taken along line I-I′ of FIGS. 11, 13, 15, 17, 19,21, 23, 25, 27, 29, 31, and 33 , respectively.

FIG. 35 is a schematic plan view of a display apparatus according to anexemplary embodiment.

FIG. 36 is a schematic cross-sectional view of a light emitting diodepixel for a display according to an exemplary embodiment.

FIG. 37 is a schematic circuit diagram of a display apparatus accordingto an exemplary embodiment.

FIG. 38 is a schematic plan view of a display apparatus according to anexemplary embodiment.

FIG. 39 is an enlarged plan view of one pixel of the display apparatusof FIG. 38 .

FIG. 40A is a schematic cross-sectional view taken along line A-A ofFIG. 39 .

FIG. 40B is a schematic cross-sectional view taken along line B-B ofFIG. 39 .

FIG. 40C is a schematic cross-sectional view taken along line C-C ofFIG. 39 .

FIG. 40D is a schematic cross-sectional view taken along line D-D ofFIG. 39 .

FIGS. 41A, 41B, 41C, 42A, 42B, 43A, 43B, 44A, 44B, 45A, 45B, 46A, 46B,47A, 47B, 48A, 48B, 49A, 49B, 50A, 50B, 51, 52A, 52B, and 53 areschematic plan view and cross-sectional views illustrating a method ofmanufacturing a display apparatus according to an exemplary embodiment.

FIG. 54 is a schematic cross-sectional view of a display apparatusaccording to another exemplary embodiment.

DETAILED DESCRIPTION

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of various exemplary embodiments or implementations of theinvention. As used herein “embodiments” and “implementations” areinterchangeable words that are non-limiting examples of devices ormethods employing one or more of the inventive concepts disclosedherein. It is apparent, however, that various exemplary embodiments maybe practiced without these specific details or with one or moreequivalent arrangements. In other instances, well-known structures anddevices are shown in block diagram form in order to avoid unnecessarilyobscuring various exemplary embodiments. Further, various exemplaryembodiments may be different, but do not have to be exclusive. Forexample, specific shapes, configurations, and characteristics of anexemplary embodiment may be used or implemented in another exemplaryembodiment without departing from the inventive concepts.

Unless otherwise specified, the illustrated exemplary embodiments are tobe understood as providing exemplary features of varying detail of someways in which the inventive concepts may be implemented in practice.Therefore, unless otherwise specified, the features, components,modules, layers, films, panels, regions, and/or aspects, etc.(hereinafter individually or collectively referred to as “elements”), ofthe various embodiments may be otherwise combined, separated,interchanged, and/or rearranged without departing from the inventiveconcepts.

The use of cross-hatching and/or shading in the accompanying drawings isgenerally provided to clarify boundaries between adjacent elements. Assuch, neither the presence nor the absence of cross-hatching or shadingconveys or indicates any preference or requirement for particularmaterials, material properties, dimensions, proportions, commonalitiesbetween illustrated elements, and/or any other characteristic,attribute, property, etc., of the elements, unless specified. Further,in the accompanying drawings, the size and relative sizes of elementsmay be exaggerated for clarity and/or descriptive purposes. When anexemplary embodiment may be implemented differently, a specific processorder may be performed differently from the described order. Forexample, two consecutively described processes may be performedsubstantially at the same time or performed in an order opposite to thedescribed order. Also, like reference numerals denote like elements.

When an element, such as a layer, is referred to as being “on,”“connected to,” or “coupled to” another element or layer, it may bedirectly on, connected to, or coupled to the other element or layer orintervening elements or layers may be present. When, however, an elementor layer is referred to as being “directly on,” “directly connected to,”or “directly coupled to” another element or layer, there are nointervening elements or layers present. To this end, the term“connected” may refer to physical, electrical, and/or fluid connection,with or without intervening elements. Further, the D1-axis, the D2-axis,and the D3-axis are not limited to three axes of a rectangularcoordinate system, such as the x, y, and z—axes, and may be interpretedin a broader sense. For example, the D1-axis, the D2-axis, and theD3-axis may be perpendicular to one another, or may represent differentdirections that are not perpendicular to one another. For the purposesof this disclosure, “at least one of X, Y, and Z” and “at least oneselected from the group consisting of X, Y, and Z” may be construed as Xonly, Y only, Z only, or any combination of two or more of X, Y, and Z,such as, for instance, XYZ, XYY, YZ, and ZZ. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

Although the terms “first,” “second,” etc. may be used herein todescribe various types of elements, these elements should not be limitedby these terms. These terms are used to distinguish one element fromanother element. Thus, a first element discussed below could be termed asecond element without departing from the teachings of the disclosure.

Spatially relative terms, such as “beneath,” “below,” “under,” “lower,”“above,” “upper,” “over,” “higher,” “side” (e.g., as in “sidewall”), andthe like, may be used herein for descriptive purposes, and, thereby, todescribe one elements relationship to another element(s) as illustratedin the drawings. Spatially relative terms are intended to encompassdifferent orientations of an apparatus in use, operation, and/ormanufacture in addition to the orientation depicted in the drawings. Forexample, if the apparatus in the drawings is turned over, elementsdescribed as “below” or “beneath” other elements or features would thenbe oriented “above” the other elements or features. Thus, the exemplaryterm “below” can encompass both an orientation of above and below.Furthermore, the apparatus may be otherwise oriented (e.g., rotated 90degrees or at other orientations), and, as such, the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to be limiting. As used herein, thesingular forms, “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. Moreover,the terms “comprises,” “comprising,” “includes,” and/or “including,”when used in this specification, specify the presence of statedfeatures, integers, steps, operations, elements, components, and/orgroups thereof, but do not preclude the presence or addition of one ormore other features, integers, steps, operations, elements, components,and/or groups thereof. It is also noted that, as used herein, the terms“substantially,” “about,” and other similar terms, are used as terms ofapproximation and not as terms of degree, and, as such, are utilized toaccount for inherent deviations in measured, calculated, and/or providedvalues that would be recognized by one of ordinary skill in the art.

Various exemplary embodiments are described herein with reference tosectional and/or exploded illustrations that are schematic illustrationsof idealized exemplary embodiments and/or intermediate structures. Assuch, variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, exemplary embodiments disclosed herein should notnecessarily be construed as limited to the particular illustrated shapesof regions, but are to include deviations in shapes that result from,for instance, manufacturing. In this manner, regions illustrated in thedrawings may be schematic in nature and the shapes of these regions maynot reflect actual shapes of regions of a device and, as such, are notnecessarily intended to be limiting.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure is a part. Terms,such as those defined in commonly used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe context of the relevant art and should not be interpreted in anidealized or overly formal sense, unless expressly so defined herein.

Hereinafter, exemplary embodiments of the present disclosure will beexplained in detail with reference to the accompanying drawings. As usedherein, a light emitting stacked structure or a light emitting diodeaccording to exemplary embodiments may include a micro LED, which has asurface area less than about 10,000 square μm as known in the art. Inother exemplary embodiments, the micro LED's may have a surface area ofless than about 4,000 square μm, or less than about 2,500 square μm,depending upon the particular application.

FIG. 1 is a cross-sectional view of a light emitting stacked structureaccording to an exemplary embodiment.

Referring to FIG. 1 , the light emitting stacked structure according toan exemplary embodiment includes a plurality of epitaxial stacks stackeddisposed one over another. The epitaxial stacks are disposed on asubstrate 10. The substrate 10 has substantially a plate shape with afront surface and a rear surface.

The substrate 10 may have various shapes, and the epitaxial stacks maybe disposed on a front surface of the substrate 10. The substrate 10 mayinclude an insulating material, such as a glass, a quartz, a silicon, anorganic polymer, or an organic-inorganic composite material. However,the inventive concepts are not limited to a particular material of thesubstrate 10, as long as the substrate 10 has an insulating property. Inan exemplary embodiment, a line part may be further disposed on thesubstrate 10 to apply a light emitting signal and a common voltage toeach of the epitaxial stacks. In addition, a driving device including athin film transistor may further be disposed on the substrate 10, whichmay drive the epitaxial stacks in an active matrix method. In this case,the substrate 10 may be a printed circuit board or a compositesubstrate, which may be obtained by forming the line part and/or thedriving device on the glass, quartz, silicon, organic polymer, ororganic-inorganic composite material, for example.

The epitaxial stacks are sequentially stacked on the front surface ofthe substrate 10. In some exemplary embodiments, two or more epitaxialstacks emitting light having different wavelength bands from each othermay be disposed. As such, the epitaxial stack may be provided in plural,and the epitaxial stacks may emit light having different energy bandsdifferent from each other.

Each of the epitaxial stacks may have various sizes. In an exemplaryembodiment, at least one of the epitaxial stacks may have an areadifferent from the other epitaxial stacks.

When the epitaxial stacks are sequentially stacked in an upwarddirection from a lower portion, the area of the epitaxial stacks maybecome smaller along the upward direction. Among two adjacent epitaxialstacks disposed over one another, at least a portion of the upperepitaxial stack may overlap with the lower epitaxial stack. In someexemplary embodiments, the upper epitaxial stack disposed may completelyoverlap with the lower epitaxial stack, and in this case, the upperepitaxial stack may be located in an area corresponding to the lowerepitaxial stack.

In the illustrated exemplary embodiment, three epitaxial stacks aresequentially stacked on the substrate 10. The epitaxial stacks disposedon the substrate 10 may include first, second, and third epitaxialstacks 20, 30, and 40.

The first, second, and third epitaxial stacks 20, 30, and 40 may havedifferent sizes from each other. More particularly, the first, second,and third epitaxial stacks 20, 30, and 40 may have different areas fromeach other in a plan view, and the first, second, and third epitaxialstacks 20, 30, and 40 may have different widths from each other in across-sectional view. In the illustrated exemplary embodiment, the areaof the first, second, and third epitaxial stacks 20, 30, and 40gradually decreases in the order of the first epitaxial stack 20, thesecond epitaxial stack 30, and the third epitaxial stack 40. The secondepitaxial stack 30 is stacked on a portion of the first epitaxial stack20. Accordingly, a portion of the first epitaxial stack 20 is covered bythe second epitaxial stack 30, and the remaining portion of the firstepitaxial stack 20 is exposed in a plan view. The third epitaxial stack40 is stacked on a portion of the second epitaxial stack 30.Accordingly, a portion of the second epitaxial stack 30 is covered bythe third epitaxial stack 40, and the remaining portion of the secondepitaxial stack 30 is exposed in a plan view.

The area of the first, second, and third epitaxial stacks 20, 30, and 40may be changed in various ways. For example, a ratio of area between thefirst, second, and third epitaxial stacks 20, 30, and 40 may be 3:2:1,however, the inventive concepts are not limited thereto. Each of thefirst, second, and third epitaxial stacks 20, 30, and 40 may have adifferent ratio of area in consideration of an amount of light emittedfrom each epitaxial stack. For example, when the amount of light emittedfrom the third epitaxial stack 40 is small, the area ratio of the thirdepitaxial stack 40 may be relatively increased.

Each of the epitaxial stacks may emit a color light in a visible lightband among various wavelength bands. In an exemplary embodiment, lightemitted from the lowermost epitaxial stack may have the longestwavelength with the lowest energy band, and the wavelength of the colorlight emitted from the epitaxial stacks may become shorter from thelowermost to the uppermost epitaxial stacks. For example, light emittedfrom the uppermost epitaxial stack disposed may have the shortestwavelength with the highest energy band. The first epitaxial stack 20emits a first color light L1, the second epitaxial stack 30 emits asecond color light L2, and the third epitaxial stack 40 emits a thirdcolor light L3. The first, second, and third color light L1, L2, and L3may have different colors from each other, and the first, second, andthird color light L1, L2, and L3 may have different wavelength bandsfrom each other, which are sequentially shortened. In particular, thefirst, second, and third color light L1, L2, and L3 may have differentwavelength bands from each other, which gradually increases from thefirst color light L1 to the third color light L3.

In an exemplary embodiment, the first color light L1 may be red light,the second color light L2 may be green light, and the third color lightL3 may be blue light. However, the inventive concepts are not limitedthereto. When the light emitting stacked structure includes a micro LED,which has a surface area less than about 10,000 square μm as known inthe art, or less than about 4,000 square μm or 2,500 square μm in otherexemplary embodiments, the first epitaxial stack 20 may emit any one ofred, green, and blue light, and the second and third epitaxial stacks 30and 40 may emit a different one of red, green, and blue light, withoutadversely affecting operation, due to the small form factor of a microLED.

Each epitaxial stack emits light in a direction away from the substrate10 faces. In this case, light from one epitaxial stack may be emitteddirectly to the outside in a direction away from the substrate 10, oremitted through an upper epitaxial stack disposed in an optical path.The direction away from the substrate 10 may indicate a direction inwhich the first, second, and third epitaxial stacks 20, 30, and 40 arestacked. Hereinafter, the direction away from the substrate will bereferred to as a “front surface direction” or an “upward direction”, anda direction towards the substrate 10 faces will be referred to as a“rear surface direction” or a “downward direction”. However, terms“upward” and “downward” are relative terms, which may vary depending onan arrangement or a stacked direction of the light emitting stackedstructure.

Each epitaxial stack emits light towards the upward direction. Lightemitted from each epitaxial stack may directly travel in the upwarddirection or through another epitaxial stack disposed thereabove. In anexemplary embodiment, a first portion of light emitted from the firstepitaxial stack 20 directly travels in the upward direction through theexposed upper surface thereof, a second portion of light emitted fromthe first epitaxial stack 20 travels in the upward direction afterpassing through the second epitaxial stack 30, and a third portion ofthe light emitted from the first epitaxial stack 20 travels in theupward direction after passing through the second and third epitaxialstacks 30 and 40. A portion of light emitted from the second epitaxialstack 30 directly travels in the upward direction through the exposedupper surface thereof, and the other portion of the light emitted fromthe second epitaxial stack 30 travels in the upward direction afterpassing through the third epitaxial stack 40. Light emitted from thethird epitaxial stack 40 directly travels in the upward direction.

Each epitaxial stack may transmit most of light emitted from theepitaxial stack disposed thereunder. In particular, the portion of lightemitted from the first epitaxial stack 20 travels in the front surfacedirection after passing through the second epitaxial stack 30 and thethird epitaxial stack 40, and the portion of light emitted from thesecond epitaxial stack 30 travels in the front surface direction afterpassing through the third epitaxial stack 40. As such, at least aportion or an entire portion of other epitaxial stacks except for thelowermost epitaxial stack may be formed of a light transmittingmaterial. As used herein, the term “light transmitting material” mayrefer to a material transmitting an entire light or a materialtransmitting a predetermined wavelength or a portion of light having apredetermined wavelength. In an exemplary embodiment, each epitaxialstack may transmit about 60% or more of light emitted from the epitaxialstack disposed thereunder. According to another exemplary embodiment,each epitaxial stack may transmit about 80% or more of light from theepitaxial stack disposed thereunder, and according to another exemplaryembodiment, each epitaxial stack may transmit about 90% or more of lightfrom the epitaxial stack disposed thereunder.

According to an exemplary embodiment, the epitaxial stacks may beindependently driven as signal lines that respectively apply lightemitting signals to the epitaxial stacks are independently connected tothe epitaxial stacks, and thus, may display various colors depending onwhether light is emitted from each epitaxial stack. In addition, sincethe epitaxial stacks emitting light having difference wavelengths areformed to be overlapped with each other, the light emitting stackedstructure may be formed in a narrow area.

FIG. 2 is a cross-sectional view of a light emitting stacked structurean exemplary embodiment.

Referring to FIG. 2 , the light emitting stacked structure according toan exemplary embodiment includes the first, second, and third epitaxialstacks 20, 30, and 40 disposed on the substrate 10, with first, second,and third adhesive layers 61, 63, and 65 therebetween. The firstadhesive layer 61 may include a conductive or non-conductive material.In some exemplary embodiments, the first adhesive layer 61 may have aconductivity at portions thereof to be electrically connected to thesubstrate 10 disposed thereunder. The first adhesive layer 61 mayinclude a transparent or non-transparent material. When the substrate 10includes the non-transparent material and the line part is formed on thesubstrate 10, the first adhesive layer 61 may include thenon-transparent material, for example, a light absorbing material, suchas an epoxy-based polymer adhesive.

The second and third adhesive layers 63 and 65 may include anon-conductive material and may include a light transmitting material.For example, the second and third adhesive layers 63 and 65 may includean optically clear adhesive (OCA). However, the inventive concepts arenot limited to a particular material of the second and third adhesivelayers 63 and 65, as long as the second and third adhesive layers 63 and65 are optically clear and stably attach each epitaxial stack. Forexample, the second and third adhesive layers 63 and 65 may include anorganic material, such as an epoxy-based polymer like SU-8, variousresists, parylene, poly(methyl methacrylate) (PMMA), benzocyclobutene(BCB), and spin on glass (SOG), and an inorganic material, such assilicon oxide and aluminum oxide. In some exemplary embodiments, aconductive oxide may be used as the adhesive layer, and in this case,the conductive oxide may be insulated from other components. When theorganic material is used as the adhesive layer, the first, second, andthird epitaxial stacks 20, 30, and 40 and the substrate 10 may beattached to each other by coating the material on an adhesive side ofthe first, second, and third epitaxial stacks 20, 30, and 40 and thesubstrate 10, and applying a high temperature and a high pressure to thematerial under a high vacuum state. When the inorganic material is usedas the adhesive layer, the first, second, and third epitaxial stacks 20,30, and 40 and the substrate 10 may be attached to each other bydepositing the material on the adhesive side of the first, second, andthird epitaxial stacks 20, 30, and 40 and the substrate 10, planarizingthe material using a chemical-mechanical planarization (CMP), performinga plasma treatment on a surface of the material, and attaching under thehigh vacuum state, for example. Each of the first, second, and thirdepitaxial stacks 20, 30, and 40 includes a p-type semiconductor layer25, 35, and 45, an active layer 23, 33, and 43, and an n-typesemiconductor layer 21, 31, and 41, which are sequentially stacked.

The p-type semiconductor layer 25, the active layer 23, and the n-typesemiconductor layer 21 of the first epitaxial stack 20 may include asemiconductor material that emits red light, such as aluminum galliumarsenide (AlGaAs), gallium arsenide phosphide (GaAsP), aluminum galliumindium phosphide (AlGaInP), and gallium phosphide (GaP), etc., withoutbeing limited thereto.

A first p-type contact electrode layer 25 p may be disposed under thep-type semiconductor layer 25 of the first epitaxial stack 20. The firstp-type contact electrode layer 25 p of the first epitaxial stack 20 mayhave a single-layer structure or a multi-layer structure and may includemetal. For example, the first p-type contact electrode layer 25 p mayinclude metal, such as Al, Ti, Cr, Ni, Au, Ag, Sn, W, Cu, or an alloythereof. The first p-type contact electrode layer 25 p may include metalhaving high reflectance to improve light emission efficiency in theupward direction by the reflecting light emitted from the firstepitaxial stack 20.

A first n-type contact electrode 21 n may be disposed on the n-typesemiconductor layer of the first epitaxial stack 20. The first n-typecontact electrode 21 n of the first epitaxial stack 20 may have asingle-layer structure or a multi-layer structure and may include metal.For example, the first n-type contact electrode 21 n may include metal,such as Al, Ti, Cr, Ni, Au, Ag,

Sn, W, Cu, or an alloy thereof. However, the inventive concepts are notlimited thereto, and other conductive materials may be used.

The second epitaxial stack 30 includes the p-type semiconductor layer35, the active layer 33, and the n-type semiconductor layer 31, whichare sequentially stacked. The p-type semiconductor layer 35, the activelayer 33, and the n-type semiconductor layer 31 may include asemiconductor material that may emit green light, such as indium galliumnitride (InGaN), gallium nitride (GaN), gallium phosphide (GaP),aluminum gallium indium phosphide (AlGaInP), and aluminum galliumphosphide (AlGaP), for example, without being limited thereto.

A second p-type contact electrode layer 35 p is disposed under thep-type semiconductor layer 35 of the second epitaxial stack 30. Thesecond p-type contact electrode layer 35 p is disposed between the firstepitaxial stack 20 and the second epitaxial stack 30, in detail, betweenthe second adhesive layer 63 and the second epitaxial stack 30.

A second n-type contact electrode 31 n may be disposed on the n-typesemiconductor layer of the second epitaxial stack 30. The second n-typecontact electrode 31 n of the second epitaxial stack 30 may have asingle-layer structure or a multi-layer structure, and may includemetal. For example, the second n-type contact electrode 31 n may includemetal, such as Al, Ti, Cr, Ni, Au, Ag, Sn, W, Cu, or an alloy thereof.However, the inventive concepts are not limited thereto, and otherconductive materials may be used.

The third epitaxial stack 40 includes the p-type semiconductor layer 45,the active layer 43, and the n-type semiconductor layer 41, which aresequentially stacked. The p-type semiconductor layer 45, the activelayer 43, and the n-type semiconductor layer 41 may include asemiconductor material that may emit blue light, such as gallium nitride(GaN), indium gallium nitride (InGaN), and zinc selenide (ZnSe), forexample, without being limited thereto.

A third p-type contact electrode layer 45 p is disposed under the p-typesemiconductor layer 45 of the third epitaxial stack 40. The third p-typecontact electrode layer 45 p is disposed between the second epitaxialstack 30 and the third epitaxial stack 40, in detail, between the thirdadhesive layer 65 and the third epitaxial stack 40.

A third n-type contact electrode 41 n may be disposed on the n-typesemiconductor layer of the third epitaxial stack 40. The third n-typecontact electrode 41 n of the third epitaxial stack 40 may have asingle-layer structure or a multi-layer structure, and may includemetal. For example, the third n-type contact electrode 41 n may includemetal, such as Al, Ti, Cr, Ni, Au, Ag, Sn, W, Cu, or an alloy thereof.However, the inventive concepts are not limited thereto, and otherconductive materials may be used.

FIG. 2 shows that each of the n-type semiconductor layers 21, 31, and 41and each of the p-type semiconductor layer 25, 35, and 45 of the first,second, and third epitaxial stacks 20, 30, and 40 has the single-layerstructure, however, in some exemplary embodiments, these layers may havea multi-layer structure and may include a superlattice layer. The activelayers 23, 33, and 43 of the first, second, and third epitaxial stacks20, 30, and 40 may have a single quantum well structure or a multiplequantum well structure.

The second p-type contact electrode layer 35 p may have an area thatsubstantially covers the second epitaxial stack 30. In addition, thethird p-type contact electrode layer 45 p may have an area thatsubstantially covers the third epitaxial stack 40. In this case, thesecond and third p-type contact electrode layers 35 p and 45 p mayinclude a transparent conductive material to transmit light emitted fromthe epitaxial stack disposed thereunder. For example, each of the secondand third p-type contact electrode layers 35 p and 45 p may include thetransparent conductive oxide (TCO), which may include tin oxide (SnO),indium oxide (InO₂), zinc oxide (ZnO), indium tin oxide (ITO), andindium tin zinc oxide (ITZO). The transparent conductive compound may bedeposited by a chemical vapor deposition (CVD) or a physical vapordeposition (PVD) using an evaporator or a sputter, for example. Thesecond and third p-type contact electrode layers 35 p and 45 p may havea thickness, e.g., from about 2000 angstroms to about 2 micrometers, soas to function as an etch stopper in the following manufacturing processwhile having a predetermined light transmittance.

In an exemplary embodiment, the first, second, and third p-type contactelectrode layers 25 p, 35 p, and 45 p may be connected to a common line.The common line is a line to which the common voltage is applied. Inaddition, light emitting signal lines may be respectively connected tothe first, second, and third n-type contact electrodes 21 n, 31 n, and41 n. In an exemplary embodiment, the common voltage Sc is applied tothe first p-type contact electrode layer 25 p, the second p-type contactelectrode layer 35 p, and the third p-type contact electrode layer 45 pthrough the common line, and the light emitting signal is applied to thefirst, second, and third n-type contact electrodes 21 n, 31 n, and 41 nthrough the light emitting signal lines. Accordingly, the first, second,and third epitaxial stacks 20, 30, and 40 may be independentlycontrolled. The light emitting signal includes first, second, and thirdlight emitting signals SR, SG, and SB respectively corresponding to thefirst, second, and third epitaxial stacks 20, 30, and 40. In anexemplary embodiment, the first, second, and third light emittingsignals SR, SG, and SB are signals respectively corresponding to lightemissions of red light, green light, and blue light.

In the illustrated exemplary embodiment, the common voltage is appliedto the p-type semiconductor layers 25, 35, and 45 of the first, second,and third epitaxial stacks 20, 30, and 40, and the light emitting signalis applied to the n-type semiconductor layers 21, 31, and 41 of thefirst, second, and third epitaxial stacks 20, 30, and 40, however, theinventive concepts are not limited thereto. For example, in someexemplary embodiments, the common voltage may be applied to the n-typesemiconductor layers 21, 31, and 41 of the first, second, and thirdepitaxial stacks 20, 30, and 40, and the light emitting signal may beapplied to the p-type semiconductor layers 25, 35, and 45 of the first,second, and third epitaxial stacks 20, 30, and 40.

The first, second, and third epitaxial stacks 20, 30, and 40 may bedriven in response to the light emitting signal applied thereto. Moreparticularly, the first epitaxial stack 20 is driven in response to thefirst light emitting signal SR, the second epitaxial stack 30 is drivenin response to the second light emitting signal SG, and the thirdepitaxial stack 40 is driven in response to the third light emittingsignal SB. In this case, the first, second and third light emittingsignals SR, SG, and SB are independently applied to the first, second,and third epitaxial stacks 20, 30, and 40, and thus, the first, second,and third epitaxial stacks 20, 30, and 40 are independently driven. Thelight emitting stacked structure may provide light having various colorsby a combination of the first, second, and third color light emittedfrom the first, second, and third epitaxial stacks 20, 30, and 40 to theupward direction.

The light emitting stacked structure having the above-describedstructure according to exemplary embodiments may have an improved lightextraction efficiency as compared to a structure having the epitaxialstacks completely overlap with each other. In particular, the amount oflight emitted from the first, second, and third epitaxial stacks 20, 30,and 40 in the upper direction without passing through other epitaxialstacks may be increased, which may improve the light extractionefficiency.

In addition, the light emitting stacked structure according to exemplaryembodiments may display various colors by a combination of differentcolors of light emitted from overlapping epitaxial stacks, rather thanproviding different color lights through different areas spaced apartfrom each other on a plane, and thus, a light emitting element accordingto exemplary embodiments may have a reduced size with increasedintegration. A conventional light emitting elements that emit differentcolors of light, e.g., red, green, and blue lights, are spaced apartfrom each other on a plane to implement a full color display.Accordingly, an area occupied by the conventional light emittingelements is relatively large since the light emitting elements arespaced apart from each other on the plane. However, light emittingelements according to exemplary embodiments that emit the differentcolors of light are disposed in the same area while being overlappedwith each other to form the light emitting stacked structure, and thus,the full color display may be implemented through a significantlysmaller area than that of the conventional art. Therefore, ahigh-resolution display device may be manufactured in a small area.

Further, even when a conventional light emitting device is manufacturedin a stacked manner, the conventional light emitting device ismanufactured by individually forming a contact part in each lightemitting element, e.g., by forming light emitting elements individuallyand separately and connecting the light emitting elements to each otherusing a wiring, which may increase the structural complexity andmanufacturing complexity. However, the light emitting stacked structureaccording to the exemplary embodiments may be manufactured bysequentially stacking plural epitaxial stacks on one substrate, formingthe contact part in the epitaxial stacks through a simplified process,and connecting the line part to the epitaxial stacks. In addition, sinceone light emitting stacked structure is mounted according to exemplaryembodiments, the manufacturing method of the display device may besignificantly simplified compared with the conventional display devicemanufacturing method, which may separately manufacture the lightemitting elements of individual colors and individually mounting thelight emitting elements.

The light emitting stacked structure according the exemplary embodimentsmay further include various components to provide high purity colorlight and high efficiency. For example, the light emitting stackedstructure may include a wavelength pass filter to prevent light having arelatively shorter wavelength from traveling towards the epitaxial stackemitting light having a relatively longer wavelength.

Hereinafter, different features and elements from those described abovewill be mainly described in order to avoid redundancy. As such, detaileddescriptions of the substantially the same elements will be omitted toavoid redundancy.

FIG. 3 is a cross-sectional of a light emitting stacked structureaccording to an exemplary embodiment.

Referring to FIG. 3 , the light emitting stacked structure may include afirst wavelength pass filter 71 disposed between the first epitaxialstack 20 and the second epitaxial stack 30.

The first wavelength pass filter 71 may selectively transmit lighthaving a predetermined wavelength. The first wavelength pass filter 71may transmit the first color light emitted from the first epitaxialstack 20 and may block or reflect light except for the first colorlight. Accordingly, the first color light emitted from the firstepitaxial stack 20 may travel in the upward direction, but the secondand third color light respectively emitted from the second and thirdepitaxial stacks 30 and 40 may not travel toward the first epitaxialstack 20 and may be reflected or blocked by the first wavelength passfilter 71.

The second and third color light may have relatively shorter wavelengthand relatively higher energy than the first color light. When the secondand third color lights are incident into the first epitaxial stack 20, asecondary light emission may be induced in the first epitaxial stack 20.According to an exemplary embodiment, however, the second and thirdcolor lights may be prevented from being incident into the firstepitaxial stack 20 by the first wavelength pass filter 71.

In an exemplary embodiment, a second wavelength pass filter 73 may bedisposed between the second epitaxial stack 30 and the third epitaxialstack 40. The second wavelength pass filter 73 may transmit the firstand second color lights respectively emitted from the first and secondepitaxial stacks 20 and 30, and may block or reflect light except forthe first and second color lights. Accordingly, the first and secondcolor lights respectively emitted from the first and second epitaxialstacks 20 and 30 may travel in the upward direction, but the third colorlight emitted from the third epitaxial stack 40 may not travel towardthe first and second epitaxial stacks 20 and 30, and may be reflected orblocked by the second wavelength pass filter 73.

The third color light has relatively shorter wavelength and relativelyhigher energy than the first and second color lights. When the thirdcolor light is incident into the first and second epitaxial stacks 20and 30, a secondary light emission may be induced in the first andsecond epitaxial stacks 20 and 30. According to an exemplary embodiment,however, the third color light may be prevented from being incident intothe first and second epitaxial stacks 20 and 30 by the second wavelengthpass filter 73.

The first and second wavelength pass filters 71 and 73 may be formed invarious ways. For example, the first and second wavelength pass filters71 and 73 may be formed by alternately stacking insulating layers havingdifferent refractive indices from each other. For example, silicondioxide (SiO₂) and titanium dioxide (TiO₂) may be alternately stacked oneach other, and a wavelength of light may be determined by adjusting athickness and/or the number of stacked layers of each of the silicondioxide (SiO₂) and the titanium dioxide (TiO₂). In some exemplaryembodiments, SiO₂, TiO₂, HfO₂, Nb₂O₅, ZrO₂, and Ta₂O₅ may be used as theinsulating layers having different refractive indices.

The light emitting stacked structure according to an exemplaryembodiment may further include various components to provide highefficiency uniform light. For example, various concave-convex portionsmay be formed on a light emitting surface. In some exemplaryembodiments, the concave-convex portions may formed on the n-typesemiconductor layer of at least one of the first, second, and thirdepitaxial stacks 20, 30, and 40, which may be a light emitting surface.

The concave-convex portion may improve a light emitting efficiency. Theconcavo-convex portion may be provided in various shapes, such as apolygonal pyramid, a hemisphere, or a surface having a roughness, onwhich concavo-convex portions are randomly arranged. The concave-convexportion may be textured through various etching processes or may beformed using a patterned sapphire substrate.

The first, second, and third color lights emitted from the first,second, and third epitaxial stacks 20, 30, and 40 may have differenceintensities, and the intensity difference may cause a difference invisibility. In an exemplary embodiment, the light emitting efficiencymay be improved by forming the concave-convex portion selectively on thelight emitting surfaces of the first, second, and third epitaxial stacks20, 30, and 40, to reduce the difference in visibility between thefirst, second, and third color lights. Since the color lightcorresponding to the red and/or blue colors has lower visibility thancolor light corresponding to green color, the difference in visibilitymay be reduced by texturing the first epitaxial stack 20 and/or thethird epitaxial stack 40. In particular, the red color light has arelatively smaller intensity as the red color light may be provided fromthe lowermost portion of the light emitting stacked structure. In thiscase, when the concave-convex portion is formed on the first epitaxialstack 20 to improve light efficiency thereof.

The light emitting stacked structure having the above-describedstructure may correspond to a light emitting element capable ofdisplaying various colors, and may be employed in a display device as apixel. Hereinafter, a display device including the light emittingstacked structure according to exemplary embodiments will be describedin more detail.

FIG. 4 is a plan view of a display device according to an exemplaryembodiment, and FIG. 5 is an enlarged plan view of portion P1 of FIG. 4.

Referring to FIGS. 4 and 5 , the display device 100 according to anexemplary embodiment may display any visual information, such as a text,a video, a photograph, and a 2D or 3D image.

The display device 100 may have various shapes, such as a closedpolygonal shape with straight sides, a circular or oval shape with acurved side, and a semi-circular or semi-oval shape with a straight sideand a curved side. In the illustrated exemplary embodiment, the displaydevice 100 will be described as having substantially a rectangularshape.

The display device 100 includes a plurality of pixels 110 that displayan image. Each pixel 110 may be a minimum unit that displays the image.Each pixel 110 may include the light emitting stacked structureaccording to an exemplary embodiment and may emit a white light and/or acolor light.

Each pixel 110 according to an exemplary embodiment includes a firstpixel 110 _(R) emitting red color light, a second pixel 110 _(G)emitting green color light, and a third pixel 110 _(B) emitting bluecolor light. The first, second, and third pixels 110 _(R), 110 _(G), and110 _(B) may respectively correspond to the first, second, and thirdepitaxial stacks 20, 30, and 40 of the light emitting stacked structuredescribed above.

The pixels 110 are arranged in a matrix form. As used herein, the pixels110 being arranged in the matrix form may refer to that the pixels 110are arranged exactly in line along rows or columns, as well as thepixels 110 being arranged substantially along the rows or columns, whiledetailed locations of the pixels 110 may be varied, e.g., a zigzag form.

FIG. 6 is a block diagram of a display device according to an exemplaryembodiment.

Referring to FIG. 6 , the display device 100 according to an exemplaryembodiment includes a timing controller 350, a scan driver 310, a datadriver 330, a line part, and the pixels. Each of the pixels isindividually connected to the scan driver 310 and the data driver 330through the line part.

The timing controller 350 receives various control signals and imagedata, which may be used to drive the display device 100, from anexternal source (e.g., an external system that transmits the imagedata). The timing controller 350 may rearrange the received image dataand apply the rearranged image data to the data driver 330. In addition,the timing controller 350 may generate scan control signals and datacontrol signals, which may be used to drive the scan driver 310 and thedata driver 330, and apply the generated scan control signals and thedata control signals to the scan driver 310 and the data driver 330,respectively.

The scan driver 310 may receive the scan control signals from the timingcontroller 350 and generate scan signals in response to the scan controlsignals.

The data driver 330 may receive the data control signals and the imagedata from the timing controller 350 and generate data signals inresponse to the data control signals.

The line part includes a plurality of signal lines. In particular, theline part includes scan lines 130 _(R), 130 _(G), and 130 _(B)(hereinafter, collectively indicated as “130”) that connect the scandriver 310 to the pixels, and data lines 120 that connect the datadriver 330 to the pixels. The scan lines 130 may be connected to thepixels, respectively, and the scan lines respectively connected to thepixels are shown in first, second and third scan lines 130 _(R), 130_(G), and 130 _(B).

In addition, the line part may further include lines that connect thetiming controller 350 and the scan driver 310, the timing controller 350and the data driver 330, or other components to each other to transmitsignals.

The scan lines 130 apply the scan signals generated by the scan driver310 to the pixels. The data signals generated by the data driver 330 areapplied to the data lines 120.

The pixels are connected to the scan lines 130 and the data lines 120.The pixels may selectively emit light in response to the data signalsprovided from the data lines 120 when the scan signals from the scanlines 103 are applied thereto. For example, each of the pixels may emitlight having the brightness that corresponds to the data signal appliedthereto during each frame period. The pixels, to which the data signalscorresponding to a black brightness are applied, may not emit lightduring corresponding frame period, and thus, displaying a black color.

In an exemplary embodiment, the pixels may be driven in a passive or anactive matrix manner. When the display device is driven in the activematrix manner, the display device 100 may be further supplied with firstand second pixel power sources, in addition to the scan signals and thedata signals.

FIG. 7 is a circuit diagram of one pixel for a passive matrix typedisplay device according to an exemplary embodiment. The pixel may beone of the pixels, e.g., the red pixel, the green pixel, and the bluepixel, and the pixel will be described with reference to the first pixel110 _(R). The second and third pixels may be driven in substantially thesame manner as the first pixel, and thus, detailed descriptions ofcircuit diagrams of the second and third pixels will be omitted to avoidredundancy.

Referring to FIG. 7 , the first pixel 110 _(R) includes a light emittingelement 150 connected between the first scan line 130 _(R) and the dataline 120. The light emitting element 150 may correspond to the firstepitaxial stack 20. When a voltage equal to or greater than a thresholdvoltage is applied to between the p-type semiconductor layer and then-type semiconductor layer, the first epitaxial stack 20 emits lighthaving the brightness that corresponds to a level of the voltage appliedthereto. As such, the light emission of the first pixel 110 _(R) may becontrolled by controlling a voltage of the scan signal applied to thefirst scan line 130 _(R) and/or a voltage of the data signal applied tothe data line 120.

FIG. 8 is a circuit diagram of one pixel for an active matrix typedisplay device according to an exemplary embodiment.

When the display device is the active matrix type display device, thefirst pixel 110 _(R) may be further supplied with first and second pixelpower sources ELVDD and ELVSS, in addition to the scan signals and thedata signals.

Referring to FIG. 8 , the first pixel 110 _(R) includes one or morelight emitting elements 150 and a transistor part connected to the lightemitting element 150.

The light emitting element 150 may correspond to the first epitaxialstack 20, the p-type semiconductor layer of the light emitting element150 may be connected to the first pixel power source ELVDD via thetransistor part, and the n-type semiconductor layer of the lightemitting element 150 may be connected to the second pixel power sourceELVSS. The first pixel power source ELVDD and the second pixel powersource ELVSS may have different electric potentials from each other. Forexample, the second pixel power source ELVSS may have an electricpotential lower than an electric potential of the first pixel powersource ELVDD by at least the threshold voltage of the light emittingelement. Each of the light emitting elements may emit light having abrightness that corresponds to a driving current controlled by thetransistor part.

The transistor part according to an exemplary embodiment includes firstand second transistors M1 and M2 and a storage capacitor Cst. However, aconfiguration of the transistor part may be variously modified.

The first transistor M1 (switching transistor) includes a sourceelectrode connected to the data line 120, a drain electrode connected toa first node N1, and a gate electrode connected to the first scan line130 _(R). The first transistor M1 is turned on to electrically connectthe data line 120 and the first node N1 when the scan signal having thevoltage sufficient to turn on the first transistor M1 is providedthrough the first scan line 130 _(R). In this case, the data signal ofthe corresponding frame is applied to the data line 120, and thus, thedata signal is applied to the first node N1. The storage capacitor Cstis charged with the data signal applied to the first node N1.

The second transistor M2 (driving transistor) includes a sourceelectrode connected to the first pixel power source ELVDD, a drainelectrode connected to the n-type semiconductor layer of the lightemitting element 150, and a gate electrode connected to the first nodeN1. The second transistor M2 controls an amount of the driving currentsupplied to the light emitting element 150 in response to the voltage ofthe first node N1.

One electrode of the storage capacitor Cst is connected to the firstpixel power source ELVDD, and the other electrode of the storagecapacitor Cst is connected to the first node N1. The storage capacitorCst is charged with the voltage corresponding to the data signal appliedto the first node N1 and maintains the charged voltage until a datasignal of a next frame is provided.

In the illustrated exemplary embodiment, the transistor part isdescribed as including two transistors as shown in FIG. 8 . However, theinventive concepts are not limited to a particular number of thetransistors included in the transistor part, and the configuration ofthe transistor part may be changed in various ways. For example, thetransistor part may include more transistors and more capacitors. Inaddition, the configurations of the first and second transistors, thestorage capacitor, and the lines are well known in the art, and thus,detailed descriptions thereof will be omitted. In some exemplaryembodiments, the configurations of the first and second transistors, thestorage capacitor, and the lines may be changed in various ways.Hereinafter, the pixel will be described with reference to a passivematrix-type pixel.

FIG. 9 is a plan view of a pixel according to an exemplary embodiment,and FIG. 10 is a cross-sectional view taken along line I-I′ of FIG. 9 .

Referring to FIGS. 9 and 10 , the pixel according to an exemplaryembodiment includes a plurality of epitaxial stacks stacked one aboveanother, and the epitaxial stacks include the first, second, and thirdepitaxial stacks 20, 30, and 40.

The first epitaxial stack 20 may have the largest area among theepitaxial stacks. The second epitaxial stack 30 has an area smaller thanthat of the first epitaxial stack 20 and is disposed on a portion of thefirst epitaxial stack 20. The third epitaxial stack 40 has an areasmaller than that of the second epitaxial stack 30 and is disposed on aportion of the second epitaxial stack 30. In the illustrated exemplaryembodiment, the first, second, and third epitaxial stacks 20, 30, and 40are arranged such that upper surfaces of the first, second, and thirdepitaxial stacks 20, 30, and 40 are sequentially exposed.

The contact part is disposed in the pixel to connect the line part tothe first, second, and third epitaxial stacks 20, 30, and 40. In someexemplary embodiments, the stacked structure of a pixel may be changeddepending on to which polarity type semiconductor layers of the first,second, and third epitaxial stacks 20, 30, and 40 the common voltage isapplied. Hereinafter, the common voltage will be described as beingapplied to the p-type semiconductor layer of the first, second, andthird epitaxial stacks 20, 30, and 40, as an example.

The first, second, and third light emitting signal lines thatrespectively apply the light emitting signals to the first, second, andthird epitaxial stacks 20, 30, and 40, and the common line that appliesthe common voltage to each of the first, second, and third epitaxialstacks 20, 30, and 40 are connected to the first, second, and thirdepitaxial stacks 20, 30, and 40. The first, second, and third lightemitting signal lines may respectively correspond to the first, second,and third scan lines 130 _(R), 130 _(G), and 130 _(B), and the commonline may correspond to the data line 120, and thus, the first, second,and third scan lines 130 _(R), 130 _(G), and 130 _(B) and the data line120 are connected to the first, second, and third epitaxial stacks 20,30, and 40.

The first, second, and third scan lines 130 _(R), 130 _(G), and 130 _(B)according to an exemplary embodiment may extend in a first direction,e.g., a horizontal direction of FIG. 9 . The data line 120 may extend ina second direction, e.g., a vertical direction of FIG. 9 , that crossesthe first, second, and third scan lines 130 _(R), 130 _(G), and 130_(B). However, the directions in which the first, second, and third scanlines 130 _(R), 130 _(G), and 130 _(B) and the data line 120 extend arenot limited thereto, and may be changed in various ways depending on thearrangement of the pixels.

Since the data line 120 and the first p-type contact electrode layer 25p are elongated in the second direction crossing the first direction,and substantially simultaneously apply the common voltage to the p-typesemiconductor layer of the first epitaxial stack 20, the data line 120and the first p-type contact electrode layer 25 p may be substantiallythe same component. As such, hereinafter, the first p-type contactelectrode layer 25 p will be referred to as the data line 120, or viceversa.

An ohmic electrodes 25 p′ is disposed in the light emitting area, inwhich the first p-type contact electrode layer 25 p is disposed, for theohmic contact between the first p-type contact electrode layer 25 p andthe first epitaxial stack 20. The ohmic electrode 25 p′ may have variousshapes and may be provided in plural. In the illustrated exemplaryembodiment, the ohmic electrode 25 p′ is disposed in an area throughwhich the lower surface of the first epitaxial stack 20 is exposed,however, the inventive concepts are not limited thereto, and the ohmicelectrode 25 p′ may be disposed at another position. The ohmic electrode25 p′ for the ohmic contact may include various materials. In anexemplary embodiment, the ohmic electrode 25 p′ corresponding to ap-type ohmic electrode 25 p′ may include an Au—Zn alloy or an Au—Bealloy. In this case, since the material for the ohmic electrode 25 p′has a reflectivity lower than that of Ag, Al, and Au, an additionalreflection electrode may be further disposed, which may include

Ag or Au, for example. In this case, a layer including Ti, Ni, Cr, or Tamay be disposed as an adhesive layer for adhesion to adjacentcomponents. For example, the adhesive layer may be deposited thinly onupper and lower surfaces of the reflection electrode including Ag or Au.

The first n-type contact electrode 21 n is disposed on the firstepitaxial stack 20. The first scan line 130 _(B) is connected to thefirst n-type contact electrode 21 n. The second n-type contact electrode31 n is disposed on the second epitaxial stack 30. The second scan line130 _(G) is connected to the second n-type contact electrode 31 n. Thethird n-type contact electrode 41 n is disposed on the third epitaxialstack 40. The third scan line 130 _(B) is connected to the third n-typecontact electrode 41 n.

A portion of one side of the second epitaxial stack 30 is removed. Asecond p-type contact electrode 35 pc is disposed on the portion fromwhich the portion of the second epitaxial stack 30 is removed. Thesecond p-type contact electrode 35 pc is connected to a first bridgeelectrode BR_(G), and the first bridge electrode BR_(G) is connected tothe data line 120 through a first contact hole CH1. A third p-typecontact electrode 45 pc is connected to a second bridge electrodeBR_(B), and the second bridge electrode BR_(B) is connected to the dataline 120 through a second contact hole CH2. Accordingly, the commonvoltage is applied to the second and third p-type contact electrodes 35pc and 45 pc through the data line 120.

In an exemplary embodiment, the first, second, and third n-type contactelectrodes 21 n, 31 n, and 41 n may include a pad part having arelatively wide area to be easily connected to the first, second, andthird scan lines 130 _(R), 130 _(G), and 130 _(B), respectively, and anextension part extending in one direction from the pad part. The padpart may have various shapes, such as substantially a circular shape,for example. The extension part may assist in providing a uniformcurrent to the n-type semiconductor layer of the first epitaxial stack20, and may extend in one direction from the pad part. The extensionpart may have various shapes, such as a substantially elongated shape,for example.

The adhesive layer, the p-type contact electrode layer, and thewavelength pass filter are disposed between the substrate 10 and each ofthe first epitaxial stack 20, the second epitaxial stack 30, and thethird epitaxial stack 40. Hereinafter, the pixel according to anexemplary embodiment will be described according to the stacking order.

The first epitaxial stack 20 is disposed on the substrate 10 with thefirst adhesive layer 61 interposed therebetween. The first epitaxialstack 20 includes the p-type semiconductor layer, the active layer, andthe n-type semiconductor layer, which are sequentially stacked in theupward direction from the lower portion.

A first insulating layer 81 is disposed on a lower surface, e.g., asurface facing the substrate 10, of the first epitaxial stack 20. Thefirst insulating layer 81 has at least one contact hole. The ohmicelectrode 25 p′ is disposed in the contact hole and makes contact withthe p-type semiconductor layer of the first epitaxial stack 20. Theohmic electrode 25 p′ may include various materials.

The ohmic electrode 25 p′ makes contact with the first p-type contactelectrode layer 25 p (e.g., the data line 120). The first p-type contactelectrode layer 25 p is disposed between the first insulating layer 81and the first adhesive layer 61.

The first p-type contact electrode layer 25 p may overlap with the firstepitaxial stack 20, more particularly, the light emitting area of thefirst epitaxial stack 20, and may cover substantial or all of the lightemitting area of the first epitaxial stack 20 in a plan view. The firstp-type contact electrode layer 25 p may include a reflective materialthat reflects light generated in the first epitaxial stack 20. Inaddition, the first insulating layer 81 may have reflectivity to enhancethe reflection of light in the first epitaxial stack 20. For example,the first insulating layer 81 may have an omni-directional reflector(ODR) structure.

More particularly, the first p-type contact electrode layer 25 p mayinclude metal having high reflectivity with respect to light emittedfrom the first epitaxial stack 20. For example, when the first epitaxialstack 20 emits red light, the first p-type contact electrode layer 25 pmay include metal, such as Au, Al, or Ag, which has high reflectivitywith respect to red light. In particular, since Au has low reflectivitywith respect to the green light and the blue light, which may be emittedfrom the second and third epitaxial stacks 30 and 40, and thus, a colormixture from light emitted by the second and third epitaxial stacks 30and 40 may be prevented.

The first n-type contact electrode 21 n is disposed on the upper surfaceof the first epitaxial stack 20. The first n-type contact electrode 21 nmay include a conductive material. In an exemplary embodiment, the firstn-type contact electrode 21 n may include various metal and alloysthereof, for example, an Au—Te alloy or an Au—Ge alloy.

The second adhesive layer 63 is disposed on the first epitaxial stack20, and the first wavelength pass filter 71, the second p-type contactelectrode layer 35 p, and the second epitaxial stack 30 are sequentiallydisposed on the second adhesive layer 63.

The first wavelength pass filter 71 covers a portion of the lightemitting area of the first epitaxial stack 20, and is disposed on aportion of the upper surface of the first epitaxial stack 20 to overlapthe area in which the second epitaxial stack 30 is disposed.

The second epitaxial stack 30 includes the p-type semiconductor layer,the active layer, and the n-type semiconductor layer, which aresequentially stacked in the upward direction.

The second epitaxial stack 30 is partially removed, and thus a portionof the second p-type contact electrode layer 35 p is exposed. The secondp-type contact electrode 35 pc is disposed on the exposed portion of thesecond p-type contact electrode layer 35 p. The second n-type contactelectrode 31 n is disposed on the second epitaxial stack 30.

The third adhesive layer 65 is disposed on the second epitaxial stack30, and the second wavelength pass filter 73, the third p-type contactelectrode layer 45 p, and the third epitaxial stack 40 are sequentiallydisposed on the third adhesive layer 65.

The second wavelength pass filter 73 covers a portion of the lightemitting area of the second epitaxial stack 30, and is disposed on aportion of the upper surface of the second epitaxial stack 30 to overlapthe area in which the third epitaxial stack 40 is disposed.

The third epitaxial stack 40 includes the p-type semiconductor layer,the active layer, and the n-type semiconductor layer, which aresequentially stacked in the upward direction.

The third epitaxial stack 40 is partially removed, and a portion of thethird p-type contact electrode layer 45 p is exposed. The third p-typecontact electrode 45 pc is disposed on the exposed portion of the thirdp-type contact electrode layer 45 p. The third n-type contact electrode41 n is disposed on the third epitaxial stack 40.

Second and third insulating layers 83 and 85 are sequentially disposedon the substrate 10 above the third epitaxial stack 40. The second andthird insulating layers 83 and 85 may include various organic/inorganicinsulating materials, without being limited thereto. For example, thesecond and/or third insulating layers 83 and 85 may include theinorganic insulating material including silicon nitride or siliconoxide, or the organic insulating material including polyimide.

The first insulating layer 81 and/or the second insulating layer 83 isprovided with contact holes to expose the upper surfaces of the firstp-type contact electrode layer 25 p, the second and third p-type contactelectrodes 35 pc and 45 pc, and the first, second, and third n-typecontact electrodes 21 n, 31 n, and 41 n. The first, second, and thirdscan lines 130 _(R), 130 _(G), and 130 _(B) are respectively connectedto the first, second, and third n-type contact electrodes 21 n, 31 n,and 41 n. The first and second bridge electrodes BR_(G) and BR_(B) areconnected to the first p-type contact electrode layer 25 p and thesecond and third p-type contact electrodes 35 pc and 45 pc through thecontact holes. In an exemplary embodiment, the second scan line 130_(G), the first bridge electrode BR_(G), and the second bridge electrodeBRB may be disposed on the first insulating layer 81, and the first andthird scan lines 130 _(R) and 130 _(B) may be disposed on the secondinsulating layer 83.

In some exemplary embodiments, a concave-convex portion may beselectively disposed on the upper surfaces of the first, second, andthird epitaxial stacks 20, 30, and 40. The concave-convex portion may bedisposed only in an area corresponding to the light emitting area or onthe entire upper surface of each semiconductor layer.

In addition, in some exemplary embodiments, a non-light transmittinglayer may be further disposed on a side portion of the second and/orthird insulating layers 83 and 85 corresponding to the side surface ofthe pixel. The non-light transmitting layer may function as a lightblocking layer to prevent light from the first, second, and thirdepitaxial stacks 20, 30, and 40 from exiting through the side surface ofthe pixel, and may include a material that absorbs or reflects light.

The non-light transmitting layer may have a single or multi-layer metal.For example, the non-light transmitting layer may include variousmaterials including a metal of Al, Ti, Cr, Ni, Au, Ag, Sn, W, and Cu oran alloy thereof.

In some exemplary embodiments, the non-light transmitting layer may bedisposed on the side surface of the second and/or third insulatinglayers 83 and 85 using the metal or the metal alloy as a separate layer.

In some exemplary embodiments, the non-light transmitting layer may beprovided by extending at least one of the first, second, and third scanlines 130 _(R), 130 _(G), and 130 _(B) and the first and second bridgeelectrodes BR_(G) and BR_(B) toward the side portion. In this case, thenon-light transmitting layer extending from at least one of the first,second, and third scan lines 130 _(R), 130 _(G), and 130 _(B) and thefirst and second bridge electrodes BR_(G) and BR_(B) may be insulatedfrom other conductive components.

In some exemplary embodiments, the non-light transmitting layer may beformed in the same process, includes the same material, and may bedisposed on the same layer as at least one of the first, second, andthird scan lines 130 _(R), 130 _(G), and 130 _(B) and the first andsecond bridge electrodes BRG and BRB, or may be provided separately fromthe first, second, and third scan lines 130 _(R), 130 _(G), and 130 _(B)and the first and second bridge electrodes BR_(G) and BR_(B).

According to another exemplary embodiment, when the non-lighttransmitting layer is not provided separately, the second and thirdinsulating layers 83 and 85 may function as the non-light transmittinglayer. In this case, the second and third insulating layers 83 and 85may not be disposed on an upper portion (e.g., the front surfacedirection) of the first, second, and third epitaxial stacks 20, 30, and40, such that light emitted from the first, second, and third epitaxialstacks 20, 30, and 40 may travel in the front surface direction.

The non-light transmitting layer according to exemplary embodiments arenot particularly limited as long as the non-light transmitting layerabsorbs or reflects light to block the transmission of light. Forexample, the non-light transmitting layer may be a distributed

Bragg reflector (DBR) dielectric mirror, a metal reflection layer formedon an insulating layer, or a black-colored organic polymer layer. Whenthe metal reflection layer is used as the non-light transmitting layer,the metal reflection layer may be in a floating state such that themetal reflection layer is electrically insulated from components ofother pixels.

In this manner, when the non-light transmitting layer is disposed on theside surface of the pixel, light may be prevented from exiting through aside surface thereof, such that one pixel may not influence a pixeladjacent thereto and mixing of light between adjacent pixels may beprevented.

The pixel according to the exemplary embodiments may be manufactured bysequentially stacking the first, second, and third epitaxial stacks 20,30, and 40 on the substrate 10, which will be described hereinafter.

FIGS. 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, and 33 are plan viewsof a substrate on which first, second, and third epitaxial stacks aresequentially stacked. FIGS. 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32,and 34 are cross-sectional views taken along line I-I′ of FIGS. 11, 13,15, 17, 19, 21, 23, 25, 27, 29, 31, and 33 , respectively.

Referring to FIGS. 11 and 12 , the first, second, and third epitaxialstacks 20, 30, and 40 are sequentially formed on the substrate 10.

In particular, the first epitaxial stack 20 and the ohmic electrode 25p′ are formed on a first temporary substrate. The first temporarysubstrate may be a semiconductor substrate, e.g., a gallium arsenide(GaAs) substrate, on which the first epitaxial stack 20 may be grown.The first epitaxial stack 20 is manufactured by forming the n-typesemiconductor layer, the active layer, and the p-type semiconductorlayer on the first temporary substrate. The first insulating layer 81including a contact hole is formed on the first temporary substrate, andthe ohmic electrode 25 p′ is formed in the contact hole of the firstinsulating layer 81.

The ohmic electrode 25 p′ may be formed by forming the first insulatinglayer 81 on the first temporary substrate, coating a photoresist,patterning the photoresist, depositing a material for the ohmicelectrode 25 p′ on the patterned photoresist, and lifting off thephotoresist pattern, for example. In some exemplary embodiments, theohmic electrode 25 p′ may be formed by forming the first insulatinglayer 81, patterning the first insulating layer 81 using aphotolithography process, forming a layer for the ohmic electrode 25 p′using the material for the ohmic electrode 25 p′, and patterning thelayer for the ohmic electrode 25 p′ using a photolithography process.

The first p-type contact electrode layer 25 p, e.g., the data line 120,is formed on the first temporary substrate on which the ohmic electrode25 p′ is formed. The first p-type contact electrode layer 25 p mayinclude a reflective material. The first p-type contact electrode layer25 p may be formed by depositing a metal material on the first temporarysubstrate and patterning the deposited metal material using aphotolithography process.

The first epitaxial stack 20 formed on the first temporary substrate isinversely attached to the substrate 10 with the first adhesive layer 61interposed therebetween.

The first temporary substrate is removed after the first epitaxial stack20 is attached to the substrate 10. The first temporary substrate may beremoved by various methods, such as a wet etch process, a dry etchprocess, a physical removal process, or a laser lift-off process.

After the first temporary substrate is removed, the first n-type contactelectrode 21 n is formed on the first epitaxial stack 20. The firstn-type contact electrode 21 n may be formed by forming a conductivematerial and patterning the conductive material using a photolithographyprocess or the like.

In some exemplary embodiments, a concave-convex portion may be formed onthe upper surface (n-type semiconductor layer) of the first epitaxialstack 20 after the first temporary substrate is removed. Theconcave-convex portion may be textured through various etchingprocesses. For example, the concave-convex portion may be formed throughvarious processes, such as a dry etch process using a microphotography,a wet etch process using crystal properties, a texturing process using aphysical method such as a sandblast, an ion beam etch process, or atexturing process using an etching rate difference of block copolymer.

The second epitaxial stack 30, the second p-type contact electrode layer35 p, and the first wavelength pass filter 71 are formed on a secondtemporary substrate.

The second temporary substrate may be a sapphire substrate. The secondepitaxial stack 30 may be manufactured by forming the n-typesemiconductor layer, the active layer, and the p-type semiconductorlayer on the second temporary substrate.

The second epitaxial stack 30 formed on the second temporary substrateis inversely attached to the first epitaxial stack 20 with the secondadhesive layer 63 interposed therebetween. The second temporarysubstrate is removed after the second epitaxial stack 30 is attached tothe first epitaxial stack 20. The second temporary substrate may beremoved by various methods, such as a wet etch process, a dry etchprocess, a physical removal process, or a laser lift-off process. Insome exemplary embodiments, a concave-convex portion may be formed onthe upper surface (n-type semiconductor layer) of the second epitaxialstack 30 after the second temporary substrate is removed. Theconcave-convex portion may be textured through various etching processesor may be formed using the patterned sapphire substrate as the secondtemporary substrate.

The third epitaxial stack 40, the third p-type contact electrode layer45 p, and the second wavelength pass filter 73 are formed on a thirdtemporary substrate.

The third temporary substrate may be a sapphire substrate. The thirdepitaxial stack 40 may be manufactured by forming the n-typesemiconductor layer, the active layer, and the p-type semiconductorlayer on the third temporary substrate.

The third epitaxial stack 40 formed on the third temporary substrate isinversely attached to the second epitaxial stack 30 with the thirdadhesive layer 65 interposed therebetween. The third temporary substrateis removed after the third epitaxial stack 40 is attached to the secondepitaxial stack 30. The third temporary substrate may be removed byvarious methods, such as a wet etch process, a dry etch process, aphysical removal process, or a laser lift-off process. In some exemplaryembodiments, a concave-convex portion may be formed on the upper surface(n-type semiconductor layer) of the third epitaxial stack 40 after thethird temporary substrate is removed. The concave-convex portion may betextured through various etching processes or may be formed using thepatterned sapphire substrate as the second temporary substrate.

The third n-type contact electrode 41 n is formed on the upper surfaceof the third epitaxial stack 40. The third n-type contact electrode 41 nmay be formed by forming a conductive material layer on the uppersurface of the third epitaxial stack 40 and patterning the conductivematerial layer using a photolithography process, for example.

Referring to FIGS. 13 and 14 , the third epitaxial stack 40 ispatterned. A portion of the third epitaxial stack 40 is removed from apredetermined area of the pixel such that the third epitaxial stack 40has the area smaller than the first and second epitaxial stacks 20 and30 to be formed later. In addition, the third epitaxial stack 40 is alsoremoved from an area in which the third p-type contact electrode 45 pcis to be formed. The third epitaxial stack 40 may be removed by variousmethods, such as the wet etch process or the dry etch process, using thephotolithography process, and in this case, the third p-type contactelectrode layer 45 p acts as an etch stopper.

Referring to FIGS. 15 and 16 , the third p-type contact electrode 45 pcis formed on a portion of the third p-type contact electrode layer 45 pexposed from removing the third epitaxial stack 40. The third p-typecontact electrode 45 pc may be formed by forming a conductive materiallayer on the upper surface of the substrate 10, on which the thirdp-type contact electrode layer 45 p is formed, and patterning theconductive material layer using a photolithography process.

Referring to FIGS. 17 and 18 , portions of the third p-type contactelectrode layer 45 p, the second wavelength pass filter 73, and thethird adhesive layer 65 are removed from an area except where the thirdepitaxial stack 40 is formed. Accordingly, the upper surface of thesecond epitaxial stack 30 is exposed.

The third p-type contact electrode layer 45 p, the second wavelengthpass filter 73, and the third adhesive layer 65 may be removed byvarious methods, such as the wet etch process or the dry etch process,using the photolithography process.

Referring to FIGS. 19 and 20 , the second n-type contact electrode 31 nis formed on the exposed upper surface of the second epitaxial stack 30.The second n-type contact electrode 31 n may be formed by forming aconductive material layer on the upper surface of the second epitaxialstack 30 and patterning the conductive material layer using aphotolithography process, for example.

Referring to FIGS. 21 and 22 , the second epitaxial stack 30 ispatterned. Portions of the second epitaxial stack 30 is removed exceptfor a predetermined area of the pixel, such that the second epitaxialstack 30 has the area smaller than the first epitaxial stack 20 which isto be formed later. In addition, the second epitaxial stack 30 is alsoremoved from an area in which the second p-type contact electrode 35 pcis formed. The second epitaxial stack 30 may be removed by variousmethods, such as the wet etch process or the dry etch process, using thephotolithography process, and in this case, the second p-type contactelectrode layer 35 p acts as an etch stopper.

Referring to FIGS. 23 and 24 , the second p-type contact electrode 35 pcis formed on the second p-type contact electrode layer 35 p from whichthe portion of the second epitaxial stack 30 is removed. The secondp-type contact electrode 35 pc may be formed by forming a conductivematerial layer on the upper surface of the substrate 10, on which thesecond p-type contact electrode layer 35 p is formed, and patterning theconductive material layer using a photolithography process, for example.

The third n-type contact electrode 41 n, the third p-type contactelectrode 45 pc, the second n-type contact electrode 31 n, and thesecond p-type contact electrode 35 pc may be respectively formed throughseparate mask processes as described above, however, the inventiveconcepts are not limited thereto. More particularly, the third n-typecontact electrode 41 n is formed before the third epitaxial stack 40 ispatterned, the third p-type contact electrode 45 pc is formed after thethird epitaxial stack 40 is patterned, the second n-type contactelectrode 31 n is formed before the second epitaxial stack 30 ispatterned, and the second p-type contact electrode 35 pc is formed afterthe second epitaxial stack 30 is patterned, however the method forforming the contact electrodes may be variously modified.

For example, in some exemplary embodiments, the third n-type contactelectrode 41 n, the third p-type contact electrode 45 pc, the secondn-type contact electrode 31 n, and the second p-type contact electrode35 pc may be substantially simultaneously formed through a single maskprocess after the third epitaxial stack 40 and the second epitaxialstack 30 are sequentially patterned. When the third n-type contactelectrode 41 n and the second n-type contact electrode 31 n are formedof a different material from the third p-type contact electrode 45 pcand the second p-type contact electrode 35 pc, two types of contactelectrodes may be formed using different masks from each other. Inparticular, after the third epitaxial stack 40 and the second epitaxialstack 30 are sequentially patterned, the third n-type contact electrode41 n and the second n-type contact electrode 31 n may be substantiallysimultaneously formed through a single mask process, and the thirdp-type contact electrode 45 pc and the second p-type contact electrode35 pc may be substantially simultaneously formed through another singlemask process.

Referring to FIGS. 25 and 26 , portions of the second p-type contactelectrode layer 35 p, the first wavelength pass filter 71, and thesecond adhesive layer 63 are removed from areas except for the area inwhich the second epitaxial stack 30 is disposed. Accordingly, the uppersurface of the first epitaxial stack 20 is exposed. The second p-typecontact electrode layer 35 p, the first wavelength pass filter 71, andthe second adhesive layer 63 may be removed by various methods, such asthe wet etch process or the dry etch process, using the photolithographyprocess. Through the etch process, the first n-type contact electrode 21n disposed on the upper surface of the first epitaxial stack 20 isexposed.

Referring to FIGS. 27 and 28 , the first epitaxial stack 20 ispatterned. The first epitaxial stack 20 has the largest area among theepitaxial stacks. The first epitaxial stack 20 may be removed by variousmethods, such as the wet etch process or the dry etch process, using thephotolithography process.

In this case, the first insulating layer 81 may be substantiallysimultaneously or additionally removed, and the upper surface of thefirst p-type contact electrode 25 p, e.g., the data line, is exposed.

Referring to FIGS. 29 and 30 , the second insulating layer 83 having thecontact holes are formed on the patterned first, second, and thirdepitaxial stacks 20, 30, and 40.

The contact holes are formed at positions corresponding to the first,second, and third n-type contact electrodes 21 n, 31 n, and 41 n and thefirst to third p-type contact electrodes 25 pc, 35 pc, and 45 pc toexpose portions of the first, second, and third n-type contactelectrodes 21 n, 31 n, and 41 n and the first to third p-type contactelectrodes 25 pc, 35 pc, and 45 pc. The second insulating layer 83having the contact holes may be formed by a photolithography process,for example.

Referring to FIGS. 31 and 32 , the second scan line 130 _(G), the firstbridge electrode BR_(G), and the second bridge electrode BRB are formedon the second insulating layer 83. The second scan line 130 _(G) isconnected to the second n-type contact electrode 31 n through thecontact hole defined corresponding to the second n-type contactelectrode 31 n. One end of the first bridge electrode BR_(G) isconnected to the second p-type contact electrode 35 pc through thecontact hole defined corresponding to the second p-type contactelectrode 35 pc, and the other end of the first bridge electrode BR_(G)is connected to the first p-type contact electrode layer 25 p (e.g., thedata line 120) through the first contact hole CH1 defined above thefirst p-type contact electrode layer 25 p. One end of the second bridgeelectrode BR_(B) is connected to the third p-type contact electrode 45pc through the contact hole defined corresponding to the third p-typecontact electrode 45 pc, and the other end of the second bridgeelectrode BR_(B) is connected to the first p-type contact electrodelayer 25 p (e.g., the data line 120) through the second contact hole CH2defined above the first p-type contact electrode layer 25 p.

Referring to FIGS. 33 and 34 , the third insulating layer 85 having thecontact holes are formed on the second insulating layer 83.

The contact holes are formed at positions corresponding to the first andthird n-type contact electrodes 21 n and 41 n to expose portions of thefirst and third n-type contact electrodes 21 n and 41 n. The thirdinsulating layer 85 having the contact holes may be formed by aphotolithography process, for example.

The first and third scan lines 130 _(R) and 130 _(B) are formed on thethird insulating layer 85. The first scan lines 130 _(R) is connected tothe first n-type contact electrode 21 n through the contact hole definedcorresponding to the first n-type contact electrode 21 n. The third scanlines 130 _(B) is connected to the third n-type contact electrode 41 nthrough the contact hole defined corresponding to the third n-typecontact electrode 41 n.

In some exemplary embodiments, the sequence of forming the first,second, and third scan lines 130 _(R), 130 _(G), and 130 _(B) and thefirst and second bridge electrodes BR_(G) and BR_(B) may be variouslymodified. More particularly, while the second scan line 130 _(G) and thefirst and second bridge electrodes BR_(G) and BR_(B) are described asbeing formed through the same process, and then the first and third scanlines 130 _(R) and 130 _(B) are formed, however, in some exemplaryembodiments, the third scan line 130 _(B) may be formed after the firstand second scan lines 130 _(R) and 130 _(G) are formed through the sameprocess. As another example, the second scan line 130 _(G) may be formedafter the first and third scan lines 130 _(R) and 130 _(B) are formedthrough the same process. In addition, the first and/or second bridgeelectrodes BR_(G) and BR_(B) may be formed together with any of theoperations of forming the first, second, and third scan lines 130 _(R),130 _(G), and 130 _(B).

Further, the contact part of each of the epitaxial stacks 20, 30, and 40may be formed on different positions, and thus, the positions of thefirst, second, and third scan lines 130 _(R), 130 _(G), and 130 _(B) andthe first and second bridge electrodes BR_(G) and BR_(B) may be changed.

In some exemplary embodiments, a non-light transmitting layer may befurther disposed on the second insulating layer 83 or the thirdinsulating layer 85 in the area corresponding to the side surface of thepixel. The non-light transmitting layer may be formed by the distributedBragg reflector (DBR) dielectric mirror, the metal reflection layerformed on the insulating layer, or the organic polymer layer. When themetal reflection layer is used as the non-light transmitting layer, themetal reflection layer may be in the floating state so as to beelectrically insulated from components of other pixels. The non-lighttransmitting layer may be formed by depositing two or more insulatinglayers having different refractive indices from each other. For example,the non-light transmitting layer may be formed by sequentially stackinga material having a relatively low refractive index and a materialhaving a relatively high refractive index or by alternately stackinginsulating layers having different refractive indices from each other.The materials having different refractive indices from each other mayinclude, for example, SiO₂ and SiN_(x).

As described above, in the display device according to the exemplaryembodiments, the epitaxial stacks may be sequentially stacked, and thenthe contact with the line part may be substantially simultaneouslyformed in the epitaxial stacks.

In exemplary embodiments, the first scan line and the third scan linemay be formed through the same process, the second scan line and thethird scan line may be formed through the same process, or the first,second, and third scan lines may be formed through different processes,respectively.

FIG. 35 is a schematic plan view of a display apparatus according to anexemplary embodiment, and FIG. 36 is a schematic cross-sectional view ofa light emitting diode pixel for a display according to an exemplaryembodiment.

Referring to FIG. 35 , the display apparatus 2000 includes a supportsubstrate 251 and a plurality of pixels 200 arranged on the supportsubstrate 251. Each of the pixels 200 includes first to third subpixelsR, G, B.

Referring to FIG. 36 , the support substrate 251 supports LED stacks223, 233, 243. The support substrate 251 may include a circuit on asurface thereof or therein, but is not limited thereto. The supportsubstrate 251 may include, for example, a Si substrate or a Gesubstrate.

The first subpixel R includes a first LED stack 223, the second subpixelG includes a second LED stack 233, and the third subpixel B includes athird LED stack 243. The first subpixel R emits light through the firstLED stack 223, the second subpixel G emits light through the second LEDstack 233, and the third subpixel B emits light through the third LEDstack 243. The first to third LED stacks 223, 233, 243 can beindependently driven.

The first LED stack 223, the second LED stack 233 and the third LEDstack 243 are stacked one above another in the vertical direction so asto overlap each other. In particular, the second LED stack 233 isdisposed in some region on the first LED stack 223. As shown in thedrawings, the second LED stack 233 may be disposed towards one side onthe first LED stack 223. In addition, the third LED stack 243 isdisposed in some region on the second LED stack 233. As shown in thedrawings, the third LED stack 243 may be disposed towards one side onthe second LED stack 233. Although the second and third LED stacks 233and 243 are shown as being disposed (biased) towards the right side inthe drawings, the inventive concepts are not limited thereto, and atleast one of the second and third LED stacks 233 and 243 may be disposedtowards to the left side.

Light R generated from the first LED stack 223 may be emitted through aregion of the first LED stack 223 not covered by the second LED stack233, and light G generated from the second LED stack 233 may be emittedthrough a region of the second LED stack 233 not covered by the thirdLED stack 243. More particularly, light generated from the first LEDstack 223 may be emitted outside without passing through the second LEDstack 233 and the third LED stack 243, and light generated from thesecond LED stack 233 may be emitted outside without passing through thethird LED stack 243.

In addition, an area of a region of the first LED stack 223 throughwhich light R is emitted, an area of a region of the second LED stack233 through which light G is emitted, and an area of the third LED stackmay be different from one another, and the luminous intensity of lightemitted from each of the LED stacks 223, 233, 243 may be adjustedthrough adjustment of the light emitting areas.

Each of the first LED stack 223, the second LED stack 233 and the thirdLED stack 243 includes an n-type semiconductor layer, a p-typesemiconductor layer, and an active layer interposed therebetween. Theactive layer may have a multi-quantum well layer structure. The first tothird LED stacks 223, 233, 243 may include different active layers toemit light having different wavelengths. For example, the first LEDstack 223 may be an inorganic light emitting diode emitting red light,the second LED stack 233 may be an inorganic light emitting diodeemitting green light, and the third LED stack 243 may be an inorganiclight emitting diode emitting blue light. In this case, the first LEDstack 223 may include a GaInP-based well layer, and the second LED stack233 and the third LED stack 243 may include GaInN-based well layers.However, the inventive concepts are not limited thereto. When the pixelincludes a micro LED, which has a surface area less than about 10,000square μm as known in the art, or less than about 4,000 square μm or2,500 square μm in other exemplary embodiments, the first LED stack 223may emit any one of red, green, and blue light, and the second and thirdLED stacks 233 and 243 may emit a different one of red, green, and bluelight, without adversely affecting operation, due to the small formfactor of a micro LED. FIG. 37 is a schematic circuit diagram of adisplay apparatus according to an exemplary embodiment.

Referring to FIG. 37 , the display apparatus according to an exemplaryembodiment may be driven in a passive matrix manner. As described withreference to FIG. 35 and FIG. 36 , one pixel includes first to thirdsubpixels R, G, B. The first LED stack 223 of the first subpixel R emitslight having a first wavelength, the second LED stack 233 of the secondsubpixel G emits light having a second wavelength, and the third LEDstack 243 of the third subpixel B emits light having a third wavelength.Anodes of the first to third subpixels R, G, B may be connected to acommon line, for example, a data line Vdata 225, and cathodes thereofmay be connected to different lines, for example, scan lines Vscan 271,273, 275.

For example, in the first pixel, the anodes of the first to thirdsubpixels R, G, B are commonly connected to the data line Vdata1 and thecathodes thereof are connected to scan lines Vscan1-1, Vscan1-2,Vscan1-3, respectively. Accordingly, the subpixels R, G, B in the samepixel can be individually driven.

In addition, each of the LED stacks 223, 233, 243 may be driven by pulsewidth modulation or by changing the magnitude of electric current,thereby enabling regulation of brightness of each subpixel.Alternatively, brightness may be adjusted through adjustment of theareas of the first to third LED stacks 223, 233, 243, and the areas ofthe region of the first to third

LED stacks 223, 233, 243 through which light is emitted. For example, anLED stack emitting light having low visibility, for example, the firstLED stack 223, may be formed to have a larger area than the second LEDstack 233 or the third LED stack 243 to emit light having higherluminous intensity under the same current density. In addition, sincethe area of the second LED stack 233 is larger than the third LED stack243, the second LED stack 233 can emit light having higher luminousintensity than the third LED stack 243 under the same current density.In this manner, the luminous intensity of light emitted from the firstto third LED stacks 223, 233, 243 may be adjusted depending uponvisibility thereof by adjusting the areas of the second LED stack 233and the third LED stack 243.

FIG. 38 is a schematic plan view of a display apparatus according to anexemplary embodiment. FIG. 39 is an enlarged plan view of one pixel ofthe display apparatus shown in FIG. 38 , and FIG. 40A, FIG. 40B, FIG.40C and FIG. 40D are schematic cross-sectional views taken along linesA-A, B-B, C-C and D-D of FIG. 39 , respectively.

Referring to FIG. 38 , FIG. 39 , FIG. 40A, FIG. 40B, FIG. 40C and FIG.40D, the display apparatus 2000A according to an exemplary embodimentmay include a support substrate 251, a plurality of pixels 200A, firstto third subpixels R, G, B, a first LED stack 223, a second LED stack233, a third LED stack 243, a reflective electrode (first-2 ohmicelectrode) 225, a first-1 ohmic electrode 229, a second-1 ohmicelectrode 239, a second-2 ohmic electrode 235, a third-1 ohmic electrode249, a third-2 ohmic electrode 245, electrode pads 236, 246, a firstbonding layer 253, a second bonding layer 237, a third bonding layer247, a first transparent insulation layer 261, a first reflection layer263, a second transparent insulation layer 265, a second reflectionlayer 267, a lower insulation layer 268, an upper insulation layer 269,interconnection lines 271, 273, 275, and connecting portions 271 a, 273a, 275 a, 277 a, 277 b.

Each of the subpixels R, G, B is connected to the reflective electrode225 and the interconnection lines 271, 273, 275. As shown in FIG. 37 ,the reflective electrode 225 may be used as a data line Vdata and theinterconnection lines 271, 273, 275 may be used as scan lines Vscan.

As shown in FIG. 38 , the pixels may be arranged in a matrix, in whichanodes of the subpixels R, G, B in each pixel are commonly connected tothe reflective electrode 225 and cathodes thereof are connected to theinterconnection lines 271, 273, 275 separated from each other. Theconnecting portions 271 a, 273 a, 275 a may connect the interconnectionlines 271, 273, 275 to the subpixels R, G, B.

The support substrate 251 supports the LED stacks 223, 233, 243. Thesupport substrate 251 may include a circuit on a surface thereof ortherein, but is not limited thereto. The support substrate 251 mayinclude, for example, a glass substrate, a sapphire substrate, a Sisubstrate, or a Ge substrate.

The first LED stack 223 includes a first conductivity type semiconductorlayer 223 a and a second conductivity type semiconductor layer 223 b,the second LED stack 233 includes a first conductivity typesemiconductor layer 233 a and a second conductivity type semiconductorlayer 233 b, and the third LED stack 243 includes a first conductivitytype semiconductor layer 243 a and a second conductivity typesemiconductor layer 243 b. In addition, active layers may be interposedbetween the first conductivity type semiconductor layers 223 a, 233 a,243 a and the second conductivity type semiconductor layers 223 b, 233b, 243 b, respectively.

In an exemplary embodiment, each of the first conductivity typesemiconductor layers 223 a, 233 a, 243 a may be an n-type semiconductorlayer and each of the second conductivity type semiconductor layers 223b, 233 b, 243 b may be a p-type semiconductor layer. A roughened surfacemay be formed on a surface of at least one of the first conductivitytype semiconductor layers 223 a, 233 a, 243 a by surface texturing. Insome exemplary embodiments, the semiconductor types in each of the LEDstacks may be variously modified.

The first LED stack 223 is disposed near the support substrate 251. Thesecond LED stack 233 is disposed above the first LED stack 223, and thethird LED stack 243 is disposed above the second LED stack 233. Inaddition, the second LED stack 233 is disposed in some region on thefirst LED stack 223 such that the first LED stack 223 partially overlapsthe second LED stack 233. In addition, the third LED stack 243 isdisposed in some region on the second LED stack 233 such that second LEDstack 233 partially overlaps the third LED stack 243. Accordingly, lightgenerated from the first LED stack 223 may be emitted outside withoutpassing through the second and third LED stacks 233, 243. In addition,light generated from the second LED stack 233 may be emitted outsidewithout passing through the third LED stack 243.

Details of materials forming the first LED stack 223, the second LEDstack 233 and the third LED stack 243 are substantially the same asthose described with reference to FIG. 36 , and thus, detaileddescriptions thereof will be omitted to avoid redundancy.

The reflective electrode 225 forms ohmic contact with a lower surface ofthe first LED stack 223, in particular, the second conductivity typesemiconductor layer 223 b thereof. The reflective electrode 225 includesa reflection layer to reflect light emitted from the first LED stack223. As shown in the drawings, the reflective electrode 225 may coversubstantially the entire lower surface of the first LED stack.Furthermore, the reflective electrode 225 may be commonly connected tothe plurality of pixels 200 a and may be used as the data line Vdata.

The reflective electrode 225 may be formed of, for example, a materiallayer forming ohmic contact with the second conductivity typesemiconductor layer 223 b of the first LED stack 22,3 and may include areflection layer that may reflect light generated from the first LEDstack 223, for example, red light.

The reflective electrode 225 may include an ohmic reflection layer andmay be formed of, for example, an Au—Zn alloy or an Au—Be alloy. Thesealloys have high reflectance with respect to light in the red range andform ohmic contact with the second conductivity type semiconductor layer223 b.

The first-1 ohmic electrode 229 forms ohmic contact with the firstconductivity type semiconductor layer 223 a of the first subpixel R. Thefirst-1 ohmic electrode 229 may include a pad region and an extendedportion, and the connecting portion 275 a may be connected to the padregion of the first-1 ohmic electrode 229, as shown in FIG. 40B. Thefirst-1 ohmic electrode 229 may be spaced apart from the region wherethe second LED stack 233 is disposed.

The second-1 ohmic electrode 239 forms ohmic contact with the firstconductivity type semiconductor layer 233 a of the second LED stack 233.The second-1 ohmic electrode 239 may also include a pad region and anextended portion, and the connecting portion 273 a may be connected tothe pad region of the second-1 ohmic electrode 239, as shown in FIG.40C. The second-1 ohmic electrode 239 may be spaced apart from theregion in which the third LED stack 243 is disposed.

The second-2 ohmic electrode 235 forms ohmic contact with the secondconductivity type semiconductor layer 233 b of the second LED stack 233.The second-2 ohmic electrode 235 may include a reflection layerreflecting light generated from the second LED stack 233. For example,the second-2 ohmic electrode 235 may include a metal reflection layer.

The electrode pad 236 may be formed on the second-2 ohmic electrode 235.The electrode pad 236 is restrictively disposed on a portion of thesecond-2 ohmic electrode 235, and the connecting portion 277 b may beconnected to the electrode pad 236.

The third-1 ohmic electrode 249 forms ohmic contact with the firstconductivity type semiconductor layer 243 a of the third LED stack 243.The third-1 ohmic electrode 249 may also include a pad region and anextended portion, and the connecting portion 271 a may be connected tothe pad region of the third-1 ohmic electrode 249, as shown in FIG. 40D.

The third-2 ohmic electrode 245 forms ohmic contact with the secondconductivity type semiconductor layer 243 b of the third LED stack 243.The third-2 ohmic electrode 245 may include a reflection layerreflecting light generated from the third LED stack 233. For example,the third-2 ohmic electrode 245 may include a metal layer.

The electrode pad 246 may be formed on the third-2 ohmic electrode 245.The electrode pad 246 is restrictively disposed on a portion of thethird-2 ohmic electrode 245, and the connecting portion 277 a may beconnected to the electrode pad 246.

The reflective electrode 225, the second-2 ohmic electrode 235, and thethird-2 ohmic electrode 245 may assist in current spreading throughohmic contact with the p-type semiconductor layer of each LED stack. Thefirst-1 ohmic electrode 229, the second-1 ohmic electrode 239 and thethird-1 ohmic electrode 249 may assist in current spreading throughohmic contact with the n-type semiconductor layer of each LED stack.

The first bonding layer 253 couples the first LED stack 223 to thesupport substrate 251. As shown in the drawings, the reflectiveelectrode 225 may adjoin the first bonding layer 253. The first bondinglayer 253 may be a light transmissive or opaque layer. The first bondinglayer 253 may be formed of organic or inorganic materials. Examples ofthe organic materials may include SUB, poly(methyl methacrylate) (PMMA),polyimide, Parylene, benzocyclobutene (BCB), or others, and examples ofthe inorganic materials may include Al₂O₃, SiO₂, SiN_(x), or others. Theorganic material layers may be bonded under high vacuum and highpressure conditions, and the inorganic material layers may be bondedunder high vacuum after changing surface energy using plasma through,for example, chemical mechanical polishing, to flatten the surfaces ofthe inorganic material layers. In particular, a bonding layer formed ofa black epoxy resin capable of absorbing light may be used as the firstbonding layer 253, thereby improving contrast of a display apparatus.The first bonding layer 253 may be formed of spin-on-glass, for example.

The first reflection layer 263 is interposed between the first LED stack223 and the second LED stack 233. The first reflection layer 263reflects light generated from the first LED stack 223 and travelingtowards the second LED stack 233 back to the first LED stack 223. Thelight reflected back to the first LED stack 223 may be emitted outsidethrough a region not covered by the second LED stack 233. In thismanner, the first reflection layer 263 prevents light generated from thefirst LED stack 223 from entering and being absorbed by the second LEDstack 233, thereby improving light extraction efficiency of the firstLED stack 223. The first reflection layer 263 may include a metal layerhaving high reflectance with respect to light generated from the firstLED stack 223, and may include, for example, an Au layer, an Al layer,or an Ag layer.

The second reflection layer 267 is interposed between the second LEDstack 233 and the third LED stack 243. The second reflection layer 267reflects light generated from the second LED stack 233 and travelingtowards the third LED stack 243 back to the second LED stack 233. Thelight reflected back to the second LED stack 233 may be emitted outsidethrough a region not covered by the third LED stack 243. In this manner,the second reflection layer 267 prevents light generated from the secondLED stack 233 from entering and being absorbed by the third LED stack243, thereby improving light extraction efficiency of the second LEDstack 233. The second reflection layer 267 may include a metal layerhaving high reflectance with respect to light generated from the secondLED stack 233, and may include, for example, an Au layer, an Al layer,or an Ag layer.

The first transparent insulation layer 261 is interposed between thefirst reflection layer 263 and the first LED stack 223. The firsttransparent insulation layer 261 insulates the first reflection layer263 from the first LED stack 223. In addition, the first transparentinsulation layer 261 may include a dielectric layer, such as SiO₂, whichhave a lower index of refraction than the first LED stack 223.Accordingly, the first LED stack 223 having a high index of refraction,the first transparent insulation layer 261 having a low index ofrefraction, and the first reflection layer 263 are sequentially stackedone above another, thereby forming an omnidirectional reflector (ODR).

The second transparent insulation layer 265 is interposed between thesecond reflection layer 267 and the second LED stack 233. The secondtransparent insulation layer 265 insulates the second reflection layer267 from the second LED stack 233. In addition, the second transparentinsulation layer 265 may include a dielectric layer, such as SiO₂, whichhas a lower index of refraction than the second LED stack 233.Accordingly, the second LED stack 233 having a high index of refraction,the second transparent insulation layer 265 having a low index ofrefraction, and the second reflection layer 267 are sequentially stackedone above another, thereby forming an omnidirectional reflector (ODR).

The second bonding layer 237 couples the first LED stack 223 to thesecond LED stack 233. The second bonding layer 237 may be interposedbetween the first reflection layer 263 and the second-2 ohmic electrode235 to bond the first reflection layer 263 to the second-2 ohmicelectrode 235. The second bonding layer 237 may include a metal bondinglayer, such as AuSn, without being limited thereto. Alternatively, thesecond bonding layer 237 may be formed of substantially the same bondingmaterial as the first bonding layer 253.

The third bonding layer 247 couples the second LED stack 233 to thethird LED stack 243. The third bonding layer 247 may be interposedbetween the second reflection layer 267 and the third-2 ohmic electrode245 to bond the second reflection layer 267 to the third-2 ohmicelectrode 245. The third bonding layer 247 may also include a metalbonding layer, such as AuSn, without being limited thereto.Alternatively, the third bonding layer 247 may be formed ofsubstantially the same bonding material as the first bonding layer 253.

The lower insulation layer 268 may cover the first to third LED stacks223, 233, 243. The lower insulation layer 268 covers the reflectiveelectrode 225 exposed around the first LED stack 223. In particular, thelower insulation layer 268 may have openings to provide electricalconnection passages.

The upper insulation layer 269 covers the lower insulation layer 268.The upper insulation layer 269 may have openings to provide electricalconnection passages.

The lower insulation layer 268 and the upper insulation layer 269 may beformed of any insulation materials, for example, silicon oxide orsilicon nitride, without being limited thereto.

As shown in FIG. 38 and FIG. 39 , the interconnection lines 271, 273,275 may be disposed to be orthogonal to the reflective electrode 225.The interconnection lines 271, 275 are disposed on the upper insulationlayer 269 and may be connected to the third-1 ohmic electrode 249 andthe first-1 ohmic electrode 229 through the connecting portions 271 a,275 a, respectively.

In an exemplary embodiment, the upper insulation layer 269 and the lowerinsulation layer 268 may have openings that expose the third-1 ohmicelectrode 249 and the first-1 ohmic electrode 229.

The interconnection line 273 is disposed on the lower insulation layer268 and is insulated from the reflective electrode 225. Theinterconnection line 273 may be disposed between the lower insulationlayer 268 and the upper insulation layer 269 and may be connected to thesecond-1 ohmic electrode 239 through the connecting portion 273 a. In anexemplary embodiment, the lower insulation layer 268 has an opening thatexposes the second-1 ohmic electrode 239.

The connecting portions 277 a, 277 b are disposed between the lowerinsulation layer 268 and the upper insulation layer 269 and electricallyconnect the electrode pads 246, 236 to the reflective electrode 225. Inan exemplary embodiment, the lower insulation layer 268 may haveopenings that expose the electrode pads 236, 246 and the reflectiveelectrode 225.

The interconnection line 271 and the interconnection line 273 areinsulated from each other by the upper insulation layer 269 and may bedisposed to overlap in the vertical direction.

The electrodes of each pixel are connected to the data line and the scanlines. In particular, the interconnection lines 271, 275 are formed onthe lower insulation layer 268 and the interconnection line 273 isdisposed between the lower insulation layer 268 and the upper insulationlayer 269. However, the inventive concepts are not limited thereto. Forexample, all of the interconnection lines 271, 273, 275 may be formed onthe lower insulation layer 268 and may be covered by the upperinsulation layer 81, and the connecting portions 271 a, 275 a may beformed on the upper insulation layer 269.

Next, a method of manufacturing the display apparatus 2000A according toan exemplary embodiment will be described.

FIG. 41 to FIG. 53 are schematic cross-sectional views illustrating amethod of manufacturing a display apparatus according to an exemplaryembodiment. Each of the cross-sectional views is taken along line A-A ofthe corresponding plan view.

First, referring to FIG. 41A, a first LED stack 223 is grown on a firstsubstrate 221. The first substrate 221 may be, for example, a GaAssubstrate. In addition, the first LED stack 223 may be formed ofAlGaInP-based semiconductor layers, and includes a first conductivitytype semiconductor layer 223 a, an active layer, and a secondconductivity type semiconductor layer 223 b.

Then, a reflective electrode 225 is formed on the first LED stack 223.The reflective electrode 225 may be formed of, for example, an Au—Znalloy or an Au—Be alloy.

The reflective electrode 225 may be formed by a lift-off process and maybe subjected to patterning to have a particular shape. For example, thereflective electrode 225 may be patterned to extend along a plurality ofpixels. However, the inventive concepts are not limited thereto.Alternatively, the reflective electrode 225 may be formed over theentire upper surface of the first LED stack 223 without patterning, ormay be subjected to patterning after formation thereon.

The reflective electrode 225 may form ohmic contact with the secondconductivity type semiconductor layer 223 b of the first LED stack 223,for example, a p-type semiconductor layer.

Referring to FIG. 41B, a second LED stack 233 is grown on a secondsubstrate 231 and a second-2 ohmic electrode 235 is formed on the secondLED stack 233. The second LED stack 233 may be formed of GaN-basedsemiconductor layers, and may include a first conductivity typesemiconductor layer 233 a, a GaInN well layer, and a second conductivitytype semiconductor layer 233 b. The second substrate 231 is a substratecapable of growing the GaN-based semiconductor layers thereon and may bedifferent from the first substrate 221. The GaInN composition of thesecond LED stack 233 may be determined such that the second LED stack233 can emit green light, for example. The second-2 ohmic electrode 235forms ohmic contact with the second conductivity type semiconductorlayer 233 b of the second LED stack 233, for example, a p-typesemiconductor layer. The second-2 ohmic electrode 235 may include areflection layer to reflect light generated from the second LED stack233.

A bonding material layer 237 a may be formed on the second-2 ohmicelectrode 235. The bonding material layer 237 a may include a metallayer, such as AuSn, without being limited thereto.

Referring to FIG. 41C, a third LED stack 243 is grown on a thirdsubstrate 41 and a third-2 ohmic electrode 245 is formed on the thirdLED stack 243. The third LED stack 243 may be formed of GaN-basedsemiconductor layers, and may include a first conductivity typesemiconductor layer 243 a, a GaInN well layer, and a second conductivitytype semiconductor layer 243 b. The third substrate 41 is a substratecapable of growing the GaN-based semiconductor layers thereon and may bedifferent from the first substrate 221. The GaInN composition of thethird LED stack 243 may be determined such that the third LED stack 243can emit blue light, for example. The third-2 ohmic electrode 245 formsohmic contact with the second conductivity type semiconductor layer 243b of the third LED stack 243, for example, a p-type semiconductor layer.The third-2 ohmic electrode 245 may include a reflection layer toreflect light generated from the third LED stack 243.

A bonding material layer 247 a may be formed on the third-2 ohmicelectrode 245. The bonding material layer 247 a may include a metallayer, such as AuSn, without being limited thereto.

The first LED stack 223, the second LED stack 233, and the third LEDstack 243 are grown on different substrates, respectively, and thesequence of forming the first to third LED stacks 223, 233, and 243 isnot particularly limited.

Referring to FIG. 42A and FIG. 42B, the first LED stack 223 of FIG. 41Ais coupled to an upper side of a support substrate 251 via a firstbonding layer 253. The reflective electrode 225 may be disposed to facethe support substrate 251 and may be bonded to the first bonding layer253. The first substrate 221 is removed from the first LED stack 223 bychemical etching or the like. As such, an upper surface of the firstconductivity type semiconductor layer 223 a of the first LED stack 223is exposed. A roughened surface may be formed on the exposed surface ofthe first conductivity type semiconductor layer 223 a by surfacetexturing, for example.

Then, a first-1 ohmic electrode 229 is formed on the exposed surface ofthe first LED stack 223. The ohmic electrode 229 may be formed of, forexample, an Au—Te alloy or an Au—Ge alloy. The ohmic electrode 229 maybe formed in each pixel region. The ohmic electrode 229 may be disposedtowards one side in each pixel region. The ohmic electrode 229 mayinclude a pad region and an extended portion, as shown in FIG. 42A.Here, the extended portion may extend substantially in the longitudinaldirection of the reflective electrode 225.

Referring to FIG. 43A and FIG. 43B, a first transparent insulation layer261 is formed on the first LED stack 223, and a first reflection layer263 is then formed thereon. As shown in the drawings, the firsttransparent insulation layer 261 may be formed to cover the first-1ohmic electrode 229, and the first reflection layer 263 may not coverthe first-1 ohmic electrode 229. However, the inventive concepts are notlimited thereto. For example, the first reflection layer 263 may coverthe first-1 ohmic electrode 229.

A bonding material layer 237 b is formed on the first reflection layer263, and the second LED stack 233 of FIG. 41B is coupled to an upperside of the bonding material layer 237 b. The bonding material layer 237a is disposed to face the support substrate 251 and is bonded to thebonding material layer 237 a to form a second bonding layer 237, bywhich the first LED stack 223 is coupled to the second LED stack 233.

The second substrate 231 is removed from the second LED stack 233 bylaser lift-off or chemical lift-off. As such, an upper surface of thefirst conductivity type semiconductor layer 233 a of the second LEDstack 233 is exposed. A roughened surface may be formed on the exposedsurface of the first conductivity type semiconductor layer 233 a bysurface texturing or the like.

Referring to FIG. 44A and FIG. 44B, first, a second transparentinsulation layer 265 is formed on the second LED stack 233, and a secondreflection layer 267 is then formed thereon. Thereafter, a bondingmaterial layer 247 b is formed on the second reflection layer 267, andthe second LED stack 233 of FIG. 42B is coupled to an upper side of thebonding material layer 247 b. The bonding material layer 247 a isdisposed to face the support substrate 251 and is bonded to the bondingmaterial layer 247 a to form a third bonding layer 247, by which thesecond LED stack 233 is coupled to the third LED stack 243.

The third substrate 41 may be removed from the third LED stack 243 bylaser lift-off or chemical lift-off. As such, an upper surface of thefirst conductivity type semiconductor layer 243 a of the third LED stack243 is exposed. A roughened surface may be formed on the exposed surfaceof the first conductivity type semiconductor layer 243 a by surfacetexturing or the like.

Next, a third-1 ohmic electrode 249 is formed on the first conductivitytype semiconductor layer 243 a. The third-1 ohmic electrode 249 may beformed towards the other side of the pixel to oppose the first-1 ohmicelectrode 229. The third-1 ohmic electrode 249 may include a pad regionand an extended portion. The extended portion may extend substantiallyin the longitudinal direction of the reflective electrode 225.

Referring to FIG. 45A and FIG. 45B, in each pixel region, the third LEDstack 243 is removed except for a region of a third subpixel B bypatterning the third LED stack 243. As such, the third-2 ohmic electrode245 is exposed, as shown in the drawings. In addition, an indentationmay be formed on the third LED stack 243 in the region for the thirdsubpixel B.

An electrode pad 246 may be formed on the third-2 ohmic electrode 245exposed to the indentation. Although the third-2 ohmic electrode 245 andthe electrode pad 246 are described as being formed by separateprocesses, in some exemplary embodiments, the third-2 ohmic electrode245 and the electrode pad 246 may be formed together by the sameprocess. For example, after the third-2 ohmic electrode 245 is exposed,the third-1 ohmic electrode 249 and the electrode pad 246 may be formedtogether by a lift-off process, for example.

Referring to FIG. 46A and FIG. 46B, in each pixel region, the third-2ohmic electrode 245, the third bonding layer 247, the second reflectionlayer 267 and the second transparent insulation layer 265 aresequentially subjected to patterning to expose the second LED stack 233.The third-2 ohmic electrode 245 is restrictively disposed near theregion for the third subpixel B.

In each pixel region, a second-1 ohmic electrode 239 is formed on thesecond LED stack 233. As shown in FIG. 46A, the second-1 ohmic electrode239 may include a pad region and an extended portion. The extendedportion may extend substantially in the longitudinal direction of thereflective electrode 225. The second-1 ohmic electrode 239 forms ohmiccontact with the first conductivity type semiconductor layer 233 a. Asshown in the drawings, the second-1 ohmic electrode 239 may be disposedbetween the first-1 ohmic electrode 229 and the third-1 ohmic electrode249, without being limited thereto.

Referring to FIG. 47A and FIG. 47B, the second LED stack 233 is removedexcept for a region of a second subpixel G in each pixel by patterningthe second LED stack 233. In the region for the second subpixel G, thesecond LED stack 233 may overlap the third LED stack 243.

As the second LED stack 233 is subjected to patterning, the second-2ohmic electrode 235 is exposed. The second LED stack 233 may include anindentation, such that the electrode pad 236 can be formed on thesecond-2 ohmic electrode 235 in the indentation.

Although the second-1 ohmic electrode 239 and the electrode pad 236 aredescribed as being formed by separate processes, in some exemplaryembodiments, the second-1 ohmic electrode 239 and the electrode pad 236may be formed together by the same process. For example, after thesecond-2 ohmic electrode 235 is exposed, the second-1 ohmic electrode239 and the electrode pad 236 may be formed together by a lift-offprocess or the like.

Referring to FIG. 48A and FIG. 48B, the second-2 ohmic electrode 235,the second bonding layer 237, the first reflection layer 263, and thefirst transparent insulation layer 261 are sequentially subjected topatterning to expose the first LED stack 223. The second-2 ohmicelectrode 235 is restrictively disposed near the region for the secondsubpixel G.

In each pixel region, the first-1 ohmic electrode 229 formed on thefirst LED stack 223 is exposed. As shown in FIG. 48B, the first-1 ohmicelectrode 229 may include a pad region and an extended portion. Theextended portion may extend substantially in the longitudinal directionof the reflective electrode 225.

Referring to FIG. 49A and FIG. 49B, the first LED stack 223 is removedexcept for a region of a first subpixel R in each pixel by patterningthe first LED stack 223. The first-1 ohmic electrode 229 may remain inthe region for the first subpixel R. The first LED stack 223 overlapsthe second LED stack 233 and the third LED stack 243. In particular, thesecond LED stack 233 and the third LED stack 243 are restrictivelydisposed in an upper region of the first LED stack 223.

As the first LED stack 223 is subjected to patterning, the reflectiveelectrode 225 is exposed and the surface of the first bonding layer 253may be partially exposed. In other exemplary embodiments, an insulationlayer may be disposed on the first bonding layer 253. In this case, theinsulation layer is exposed and the surface of the first bonding layer253 may not be exposed.

Referring to FIG. 50A and FIG. 50B, a lower insulation layer 268 isformed. The lower insulation layer 268 may cover the first to third LEDstacks 223, 233, 243, the reflective electrode 225, and the firstbonding layer 253. The lower insulation layer 268 may be subjected topatterning to form openings that expose the first-1 ohmic electrode 229,the second-1 ohmic electrode 239, the third-1 ohmic electrode 249, theelectrode pads 236, 246, and the reflective electrode 225.

Referring to FIG. 51 , an interconnection line 273 and connectingportions 273 a, 277 a, 277 b are formed on the lower insulation layer268. The connecting portion 273 a connects the second-1 ohmic electrode239 to the interconnection line 273, the connecting portion 277 aconnects the electrode pad 246 to the reflective electrode 225, and theconnecting portion 277 b connects the electrode pad 236 to thereflective electrode 225. A cross-sectional view taken along line A-A ofFIG. 51 is the same as FIG. 50B, and thus, will be omitted to avoidredundancy.

Referring to FIG. 52A and FIG. 52B, an upper insulation layer 269 isformed. The upper insulation layer 269 covers the interconnection line273 and the connecting portions 273 a, 277 a, 277 b. The upperinsulation layer 269 may be subjected to patterning to expose the padregions of the first-1 ohmic electrode 229 and the third-1 ohmicelectrode 249.

Referring to FIG. 53 , interconnection lines 271, 275 and connectingportions 271 a, 275 a are formed on the upper insulation layer 269. Theconnecting portion 271 a connects the interconnection line 271 to thethird-1 ohmic electrode 249, and the connecting portion 275 a connectsthe interconnection line 275 to the first-1 ohmic electrode 229.

In this manner, the display apparatus 2000A described with reference toFIG. 38 and FIG. 39 may be provided. A cross-sectional view taken alongline A-A of FIG. 53 is the same as FIG. 52B, and thus will be omitted toavoid redundancy.

Although the pixels are described as being driven in a passive matrixmanner in the illustrated exemplary embodiment, the inventive conceptsare not limited thereto, and the pixels may be driven in an activematrix manner in some exemplary embodiments.

FIG. 54 is a schematic cross-sectional view of a display apparatusaccording to another exemplary embodiment. Although the reflectiveelectrode 225 may be directly formed on the second conductivity typesemiconductor layer 223 b as shown in FIG. 41A, the inventive conceptsare not limited thereto.

In particular, referring to FIG. 54 , the reflective electrode 225 mayinclude an ohmic contact layer 225 a and a reflection layer 225 b. Theohmic contact layer 225 a may be formed of, for example, Au—Zn alloys orAu—Be alloys, and the reflection layer 225 b may be formed of Al, Ag orAu. When the reflection layer 225 b is formed of Au, the reflectionlayer 225 b may exhibit relatively high reflectance with respect tolight generated from the first LED stack 223, for example, red light,and may exhibit relatively low reflectance with respect to lightgenerated from the second LED stack 233 and the third LED stack 243, forexample, green light or blue light.

An insulation layer 227 may be disposed between the reflection layer 225b and the second conductivity type semiconductor layer 223 b. Theinsulation layer 227 may have openings that expose the secondconductivity type semiconductor layer 223 b, and the ohmic contact layer225 a may be formed in the openings of the insulation layer 227.

As the reflection layer 225 b covers the insulation layer 227, anomnidirectional reflector (ODR) may be formed by a stacked structure ofthe first LED stack 223 having a high index of refraction, theinsulation layer 227 having a low index of refraction, and thereflection layer 225 b.

The reflective electrode 225 may be formed by the following process.First, the first LED stack 223 is grown on the substrate 221 and theinsulation layer 227 is formed on the first LED stack 223. Then,opening(s) are formed by patterning the insulation layer 227. Forexample, SiO₂ is formed on the first LED stack 223 and a photoresist isdeposited thereon, followed by forming a photoresist pattern throughphotolithography and development. Thereafter, the SiO₂ layer issubjected to patterning using the photoresist pattern as an etchingmask, thereby forming the insulation layer 227 having the opening formedtherein.

Thereafter, the ohmic contact layer 225 a is formed in the opening(s) ofthe insulation layer 227. The ohmic contact layer 225 a may be formed bya lift-off process, for example. After formation of the ohmic contactlayer 225 a, the reflection layer 225 b is formed to cover the ohmiccontact layer 225 a and the insulation layer 227. The reflection layer225 b may be formed by a lift-off process, for example. The reflectionlayer 225 b may partially or completely cover the ohmic contact layer225 a, as shown in the drawings. The reflective electrode 225 is formedby the ohmic contact layer 225 a and the reflection layer 225 b. Theshape of the reflective electrode 225 is substantially the same as thatof the reflective electrode described above, and thus, detaileddescriptions thereof will be omitted to avoid redundancy.

Although the first LED stack 223 is described as being formed ofAlGaInP-based semiconductor layers to emit red light, however, theinventive concepts are not limited thereto. For example, the first LEDstack 223 may emit green light or blue light. In this case, the firstLED stack 223 may be formed of AlGaInN-based semiconductor layers. Inaddition, the second LED stack 233 or the third LED stack 243 may beformed of AlGaInP-based semiconductor layers.

According to the exemplary embodiments, a plurality of pixels may beformed at the wafer level by wafer bonding, thereby eliminating a needfor individual mounting of light emitting diodes.

Although certain exemplary embodiments and implementations have beendescribed herein, other embodiments and modifications will be apparentfrom this description. Accordingly, the inventive concepts are notlimited to such embodiments, but rather to the broader scope of theappended claims and various obvious modifications and equivalentarrangements as would be apparent to a person of ordinary skill in theart.

What is claimed is:
 1. A display device comprising: a substrate; a light emitting stacked structure disposed on the substrate and including a plurality of epitaxial sub-units disposed one over another; a first adhesive layer bonding the epitaxial sub-units to the substrate; and a line part disposed on the substrate and configured to apply a light emitting signal to each of the epitaxial sub-units, wherein: the light emitting stacked structure is configured to provide light having various colors by a combination of light emitted from each of the epitaxial sub-units; the first adhesive layer includes a conductive and non-transparent material; and the substrate includes a non-transparent material. 